explain xkcd - User contributions [en]

Talk:3228: Day Counter

2026-04-09T23:56:29Z

Eunakria: Addendum to my earlier question about the origin of the -0.0[...]017 thing

Someone has to be first [[Special:Contributions/2401:D005:D402:7A00:780:9D40:A38A:98A0|2401:D005:D402:7A00:780:9D40:A38A:98A0]] 13:14, 3 April 2026 (UTC)
:No, but someone has to be the ''0.99999999999999956th''... [[Special:Contributions/81.179.199.253|81.179.199.253]] 21:58, 3 April 2026 (UTC)

In response to the comment added by @[[User:GSLikesCats307|GSLikesCats307]], "When the comic was first published the number was −0.00000000000000017 days": Perhaps Randall was just trying to make things a bit more realistic. I've shown a realistic example that could generate −0.00000000000000044. My experiments didn't find any simple example that could generate −0.00000000000000017. (Which is not to say there isn't one.) —[[User:Scs|Scs]] ([[User talk:Scs|talk]]) 15:15, 3 April 2026 (UTC), edited 15:39, 4 April 2026 (UTC)

The day counter is now showing −0.00000000000000044 on my Windows 11 system using Chrome. Maybe the result differs based on computer/browser combination? [[Special:Contributions/72.218.191.213|72.218.191.213]] 16:16, 3 April 2026 (UTC)

The April Fools dark mode thing was kept! Lets go! [[User:King Pando|King Pando]] ([[User talk:King Pando|talk]]) 16:25, 3 April 2026 (UTC)

This comic was published during NASA's Artemis II moon mission. Could Cueball seeming to be floating above his chair be a reference to null gravity? [[User:PDesbeginner|PDesbeginner]] ([[User talk:PDesbeginner|talk]]) 17:12, 3 April 2026 (UTC)
:I don't think it's significant that Cueball appears to be floating. Randall sometimes draws people in chairs that way. See, for example, [[2949]], [[3015]], and [[3052]]. —[[User:Scs|Scs]] ([[User talk:Scs|talk]]) 23:25, 5 April 2026 (UTC)
::Some of the examples are also seen in What If? and What If? 2. (Yup) [[User:Cream Starlight|Cream Starlight]] ([[User talk:Cream Starlight|talk]]) 04:42, 6 April 2026 (UTC)

My guess is that irrational numbers have "infinite digits" in any base, but my math education is not good enough even to know how to start to prove it, an informal confirmation would be appreciated. [[Special:Contributions/5.91.22.162|5.91.22.162]] 22:14, 3 April 2026 (UTC)
:As a decimal in a certain base is just a fraction (with a denominator of a power of the base), numbers with finite decimal expansions must be rational (assuming the base is rational) [[User:Logalex8369|Logalex8369]] ([[User talk:Logalex8369|talk]]) 23:31, 3 April 2026 (UTC)
::Let's all work in base π so we can have irrational discussions that make sense. What's e in base π?[[Special:Contributions/98.22.184.160|98.22.184.160]] 12:49, 4 April 2026 (UTC)
:::I want to meditate on all the transcendental numbers. [[Special:Contributions/81.179.199.253|81.179.199.253]] 19:32, 4 April 2026 (UTC)

Plot twist: This is accurate, just too precise and able to predict the future. Someone is about to cause one. [[Special:Contributions/47.141.37.161|47.141.37.161]] 05:24, 4 April 2026 (UTC)
:Doesn't have to be predicting the future to be accurate. Maybe it means that the last error occurred 38 picoseconds ago. [[User:Gorcq|Gorcq]] ([[User talk:Gorcq|talk]]) 14:26, 4 April 2026 (UTC)

Surprised that there hasn't been an Artemis II comic yet. --[[User:Funstuff4fun|Funstuff4fun]] ([[User talk:Funstuff4fun|talk]]) 06:12, 4 April 2026 (UTC)

Sorry, new to posting; sorry if I am misunderstanding. The text describes −0.00000000000000044 as a very small negative number. Is this saying that it is close to zero? If so, would that be better expressed as large, rather than small? [[User:Flickerwit|Flickerwit]] ([[User talk:Flickerwit|talk]]) 15:54, 4 April 2026 (UTC)
:The value is very small. The representation of the number is large (or ''fairly'' large, by some certain limited measure). But you wouldn't call 0.9 "smaller", or 'closer to zero'/"0", than "0.8888888888..." under most usages. Even though that might be correct in a string-handling context. [[Special:Contributions/81.179.199.253|81.179.199.253]] 19:32, 4 April 2026 (UTC)
:"Greater" and "lesser" work like that (with -1 being greater than -2), but "larger" and "smaller" are more ambiguous, and often refer to the absolute value. [[Special:Contributions/192.112.253.21|192.112.253.21]] 02:58, 6 April 2026 (UTC)
::One generally would not describe −0.00000000000000044 as "large" (rather than "larger", in direct comparison), except maybe in the implicit context of numbers that routinely are orders of magnitude less (in absolute terms) ''or'' are consistently more negative (e.g. zero is an ''upper'' limit and one or other of -0.5, -5 or -5,000,000 could be more typical value).
::In the context of natural numbers, it is "small" in the grand scheme of things (or 'extremely middling', on a signum-observing basis, given how close to zero it is), especially given the implied floating precision which might suggest that 44,000,000,000,000,000 (or something not too disimilar to it — same {{w|significand}}, as above, but the most positive version of the base-exponent, not the nost negative) is another possible stored value that can be represented. [[Special:Contributions/82.132.239.70|82.132.239.70]] 12:58, 6 April 2026 (UTC)

Considering how close to April Fools this comic is, it could be a remnant of such a prank that they haven't bothered to clean up yet. [[Special:Contributions/2001:1C02:1A9D:9700:A420:F4F:966C:167E|2001:1C02:1A9D:9700:A420:F4F:966C:167E]] 16:32, 4 April 2026 (UTC)

If anyone's wondering, it appears that they made it roughly 5,879 millennia, six centuries, and one decade without an integer overflow error. [[User:DL Draco Rex|DL Draco Rex]] ([[User talk:DL Draco Rex|talk]]) 19:34, 5 April 2026 (UTC)
:...I rather think it means that it will be that long until they ''aren't'' having one. ;) [[Special:Contributions/81.179.199.253|81.179.199.253]] 21:08, 5 April 2026 (UTC)

I agree with [[User:DL Draco Rex|DL Draco Rex]]: they started a 32 bit signed integer counter on -5877585-09-23 of the [https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar# proleptic Gregorian calendar], so that the counter goes

{| class="wikitable"
|+ days since our last integer overflow.
|-
! counter !! date
|-
| 0 || -5877585-09-23
|-
| 1 || -5877585-09-24
|-
| 2 || -5877585-09-25
|-
| ... || ...
|-
| 2146743572 || -001-12-30
|-
| 2146743573 || -001-12-31
|-
| 2146743574 || 0000-01-01
|-
| 2146743575 || 0000-01-02
|-
| ... || ...
|-
| 2147483646 || 2026-04-01
|-
| 2147483647 || 2026-04-02
|-
| -2147483648 || 2026-04-03
|}

[[User:Qprz|Qprz]] ([[User talk:Qprz|talk]]) 12:59, 6 April 2026 (UTC)
:...I think year 0 technically ''does not exist''?? [[User:Cream Starlight|Cream Starlight]] ([[User talk:Cream Starlight|talk]]) 10:34, 7 April 2026 (UTC)
:: Year 0 exists in [[https://en.wikipedia.org/wiki/Astronomical_year_numbering Astronomical Year Numbering]]. Astronomer count years -1, 0, 1, 2 while historian 2BC, 1BC, 1CE, 2CE (BC is Before Christ, CE is Common Era). [[User:Qprz|Qprz]] ([[User talk:Qprz|talk]]) 20:35, 7 April 2026 (UTC)
:::If you're using "Common Era", you're probably also using "Before the Common Era", too, you know. If you're still using "Anno Domini", ''then'' it's "Before Christ". (With an alternative CE/BCE notation talking of (Before) the ''Christian'' Era, recognising the non-secular basis but with still maintaining a more secular/unaffiliated approach. They're all the same, in the long-run, but you might as well be consistant. [[Special:Contributions/81.179.199.253|81.179.199.253]] 22:49, 7 April 2026 (UTC)

<Skeletor Voice>Remember! When a company celebrates 365 days since an incident, they are celebrating the anniversary of said incident. ...Until we meet again!</Skeletor Voice> [[Special:Contributions/57.140.28.54|57.140.28.54]] 13:57, 6 April 2026 (UTC)

BTW there is an off-by-one error in the sentence

:2,147,483,647 days from the comic's date of publication (April 3rd, 2026) is approximately October 12th of the year 5,881,636.

According to numpy datetime64 we have

<pre>
>>> np.datetime64('2026-04-03', 'D') + 2147483647
np.datetime64('5881636-10-11')
</pre>

so I would rather say "2,147,483,647 days from the comic's date of publication (April 3rd, 2026) is October ''11th'' of the year 5,881,636 of the Gregorian calendar".

The computation above is exact with respect of the Gregorian calendar rules, not approximate.
Concerns about changes in the length of day (LOD) due to [[https://en.wikipedia.org/wiki/Tidal_acceleration tidal braking]] are not relevant here, since the Gregorian Calendar counts days, irrespective of their measured length in SI seconds. What matters is the discrepancy between the mean Gregorian year with respect to mean tropical year, which is also slowly changing. This discrepancy will require a calendar reform if the vernal equinox is to be kept close to the current date (March 21), in about 1200 years, see [[https://en.wikipedia.org/wiki/Tropical_year#Calendar_year Calendar Year]]. But the Gregorian Calendar is strictly algoritmical, not observational, so its extrapolation in a distant future is legitimate. [[User:Qprz|Qprz]] ([[User talk:Qprz|talk]]) 14:20, 6 April 2026 (UTC)

What is the source of the claim that the original version of the comic has -0.0[...]017? If anyone has a copy of that version, it belongs in a "Trivia" section. Until then, extraordinary claims require extraordinary evidence... [[User:Eunakria|Eunakria]] ([[User talk:Eunakria|talk]]) 22:39, 6 April 2026 (UTC)

:Hmm. I'm starting to believe actually that this was just entirely erroneous. All edits pertaining to the value of -0.0[...]017 were made by [[User:GSLikesCats307]] who has made a number of small edits with no descriptions, which is a little difficult to sort through. Relevant diffs:
:*The [https://www.explainxkcd.com/wiki/index.php?title=3228:_Day_Counter&diff=prev&oldid=409525 original edit] transcribing the comic as reading -0.0[...]017, made minutes after an [https://www.explainxkcd.com/wiki/index.php/File:day_counter_2x.png image] of the comic was uploaded to the wiki containing the figure -0.0[...]044
:*The [https://www.explainxkcd.com/wiki/index.php?title=3228:_Day_Counter&diff=prev&oldid=409529 edit] where the transcript was corrected
:*The [https://www.explainxkcd.com/wiki/index.php?title=3228:_Day_Counter&diff=prev&oldid=409558 edit] making the claim that the comic originally had the figure -0.0[...]017
:Can anyone other than [[User:GSLikesCats307]] attest to this? Or, for that matter, can [[User:GSLikesCats307]] provide an archived copy of the original image? Otherwise, I'm inclined to believe the claim should be removed.
:[[User:Eunakria|Eunakria]] ([[User talk:Eunakria|talk]]) 23:56, 9 April 2026 (UTC)

3228: Day Counter

2026-04-06T22:42:13Z

Eunakria: Mark claim that original version of this comic contained -0.0[...]017 not -0.0[...]044 with Template:actual citation needed

{{comic
| number = 3228
| date = April 3, 2026
| title = Day Counter
| image = day_counter_2x.png
| imagesize = 319x287px
| noexpand = true
| titletext = It has been −2,147,483,648 days since our last integer overflow.
}}

==Explanation==

{{incomplete|This page was created -.000000000000000032 days ago. Don't remove this notice too soon.}}

A common feature of an industrial setting is a prominent sign announcing how many days have elapsed since the last workplace accident. The sign is typically updated each day to a number one higher — or back to zero, if there ''has'' been an accident. Such signs are intended to foster a culture of safety among the workers in the facility, since presumably no one wants to suffer the embarrassment of being the one to have caused an accident that resets the number to 0. (However, it may also lead workers to cover up or conceal accidents, for the same reason, which would tend to increase future accidents, because they do not report the need to correct hazardous conditions that are causing accidents.)

In this comic, a similar sign highlights the number of days since the last floating-point error. Floating-point errors occur because most computers can devote only a finite amount of storage for each {{w|Floating-point arithmetic|floating point number}} or other fraction. However, many {{w|real numbers}} and {{w|rational numbers}} theoretically require an infinite number of digits to represent them. For example, the ordinary fraction ⅓ is represented in decimal as 0.3333333333…, where the 3s repeat forever. When a number is truncated to fit in the finite amount of space, precision is inevitably lost, resulting in a slight rounding error. Unless carefully controlled, these rounding errors can accumulate, significantly degrading the accuracy of floating-point computations. For example, although ⅓ + ⅓ + ⅓ should obviously equal 1, a finite-precision calculation like 0.333 + 0.333 + 0.333 might show a misleading result of 0.999, which might not trigger the code to do what it should do when three thirds have been accumulated (it can be mitigated by allowing a match for a value which is within a suitably very small difference to the test value, but this must be considered carefully to not be over-/under-sensitive). The amount of required space for rational numbers is not universal, it depends on the base used (⅓ in base 3 requires just two digits: 0 as the units and 1 after the {{w|Decimal separator#Radix point|radix (ternary) point}}). Floating point arithmetic standards, like the popular IEEE 754, define how and when an approximation should take place, leading to predictable results, but they don't respect some basic properties of common arithmetic operations, which someone may take for granted, e.g. in floating point arithmetic addition and multiplication are commutative (a+b=b+a; a*b=b*a), but aren't guaranteed to be associative ((a+b)+c≈a+(b+c)); (a*b)*c≈a*(b*c)).

This issue is exacerbated on computers which use binary arithmetic (i.e., virtually all computers today), since in binary, the ordinary fraction 1/10 is represented as the infinitely-repeating base-2 fraction <tt>0.000110011001100110011</tt>…. A classic example is that, depending on circumstances, the calculation 0.1 + 0.2 might [https://stackoverflow.com/questions/588004/is-floating-point-math-broken seem to give an answer of 0.30000000000000004].

Evidently, in the programming facility shown in the comic, a floating-point error has occurred today, and an attempt has been made to update the sign to say "It has been 0 days since...". But the number 0 is displayed incorrectly, as the very small negative value −0.00000000000000044. Perhaps the error that was made today was the very error that occurred in updating the sign! (This would of course violate {{w|causality}}, but in comedy, self-referential humor beats causality every time, and is at least self-consistent, like with [[363: Reset]])

As an example of how the number −0.00000000000000044 could have arisen when 0 was intended, consider this simple {{w|C (programming language)|C}} program:

#include <stdio.h>
int main()
{
double d = 19;
for(int i = 0; i < 10; i++) d -= 1.9;
printf("%.17f\n", d);
}

The program starts with the number 19, and subtracts 1.9 from it, ten times. Mathematically, we would expect the result to be 0. However, the number 1.9 cannot be represented exactly in binary, nor can the intermediate results 17.1, 15.2, 13.3, etc. The cascading roundoff errors conspire to produce a result of −0.00000000000000044 instead of the expected 0.

In the comic, such an error creates the ridiculous illusion that −0.00000000000000044 days have passed, which implies a 'negative' number of days, which is impossible{{cn}}. It also, even if it were a positive number, would mean that much less than a nanosecond had passed since the last error, which would be an unfeasably short amount of time. Of course, the joke is that in making the sign showing the amount of time since a floating point error was last made, they are creating a floating point error, meaning the sign maintains its own "error state" in a self-referential way. Also, if they tried to reset the sign, they might make the same error again, repeating the cycle over and over, which would not be ideal.

Coincidentally enough, [[Cueball]] is also floating — off his seat in this case. The seat itself looks the same as the chair in [[2144]], possibly meaning making people levitate is one of its numerous settings.

Floating point errors are particularly common in programming, especially in languages that implicitly convert decimal numbers to binary floating point, so an approximation is already made at conversion leading to unexpected results. The title text cites another common programming problem, integer overflow. When a value gets bigger than the biggest integer that can be represented in a certain format, it typically "wraps around" to the smallest value. In case of 32-bit signed integers it may wrap from 231−1 (2,147,483,647) to −231 (−2,147,483,648). 2,147,483,647 days from the comic's date of publication (April 3rd, 2026) is approximately October 12th of the year 5,881,636, assuming no changes in the lengths of the day and year, or in other aspects of time measurement.

Strangely enough, when the comic was first published the sign number was −0.00000000000000017 days.{{actual citation needed}} It was changed later though, probably so that it would be more realistic, −0.00000000000000017 would correspond to the very last bit of mantissa being incorrect and only for numbers between 1 and 2 (not including 2), and operation (1-1) is unlikely to result in rounding errors, so the smallest difference from integer is usually higher, which would result in −0.00000000000000044 the smallest possible rounding error for values between 2 and 4.

Integer overflow was the topic of [[571: Can't Sleep]], with yet another example of a 'days since' sign being [[3140: Biology Department]] (two examples, in both the comic and its title text).

It should be noted that computers displaying things like "-1 seconds until the next [blank]" is a glitch that actually happens.

==Transcript==
[White Hat, Ponytail, Cueball, and Megan are all below a large sign, which appears to be attached to the wall at its four corners. White Hat and Ponytail appear to be discussing something, while Cueball is sitting at his desk working on a laptop and Megan is walking away. The sign has text on it, as well as a large display presumably meant to show a number.]

:[Sign:] It has been
:[Display:] -0.00000000000000044
:[Sign:] days since our last floating point error

{{comic discussion}}<noinclude>[[Category:Interactive comics]][[Category:Dynamic comics]]
[[Category:Programming]]
[[Category:Math]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]

Talk:3228: Day Counter

2026-04-06T22:39:42Z

Eunakria:

Someone has to be first [[Special:Contributions/2401:D005:D402:7A00:780:9D40:A38A:98A0|2401:D005:D402:7A00:780:9D40:A38A:98A0]] 13:14, 3 April 2026 (UTC)
:No, but someone has to be the ''0.99999999999999956th''... [[Special:Contributions/81.179.199.253|81.179.199.253]] 21:58, 3 April 2026 (UTC)

In response to the comment added by @[[User:GSLikesCats307|GSLikesCats307]], "When the comic was first published the number was −0.00000000000000017 days": Perhaps Randall was just trying to make things a bit more realistic. I've shown a realistic example that could generate −0.00000000000000044. My experiments didn't find any simple example that could generate −0.00000000000000017. (Which is not to say there isn't one.) —[[User:Scs|Scs]] ([[User talk:Scs|talk]]) 15:15, 3 April 2026 (UTC), edited 15:39, 4 April 2026 (UTC)

The day counter is now showing −0.00000000000000044 on my Windows 11 system using Chrome. Maybe the result differs based on computer/browser combination? [[Special:Contributions/72.218.191.213|72.218.191.213]] 16:16, 3 April 2026 (UTC)

The April Fools dark mode thing was kept! Lets go! [[User:King Pando|King Pando]] ([[User talk:King Pando|talk]]) 16:25, 3 April 2026 (UTC)

This comic was published during NASA's Artemis II moon mission. Could Cueball seeming to be floating above his chair be a reference to null gravity? [[User:PDesbeginner|PDesbeginner]] ([[User talk:PDesbeginner|talk]]) 17:12, 3 April 2026 (UTC)

My guess is that irrational numbers have "infinite digits" in any base, but my math education is not good enough even to know how to start to prove it, an informal confirmation would be appreciated. [[Special:Contributions/5.91.22.162|5.91.22.162]] 22:14, 3 April 2026 (UTC)
:As a decimal in a certain base is just a fraction (with a denominator of a power of the base), numbers with finite decimal expansions must be rational (assuming the base is rational) [[User:Logalex8369|Logalex8369]] ([[User talk:Logalex8369|talk]]) 23:31, 3 April 2026 (UTC)
::Let's all work in base π so we can have irrational discussions that make sense. What's e in base π?[[Special:Contributions/98.22.184.160|98.22.184.160]] 12:49, 4 April 2026 (UTC)
:::I want to meditate on all the transcendental numbers. [[Special:Contributions/81.179.199.253|81.179.199.253]] 19:32, 4 April 2026 (UTC)

Plot twist: This is accurate, just too precise and able to predict the future. Someone is about to cause one. [[Special:Contributions/47.141.37.161|47.141.37.161]] 05:24, 4 April 2026 (UTC)
:Doesn't have to be predicting the future to be accurate. Maybe it means that the last error occurred 38 picoseconds ago. [[User:Gorcq|Gorcq]] ([[User talk:Gorcq|talk]]) 14:26, 4 April 2026 (UTC)

Surprised that there hasn't been an Artemis II comic yet. --[[User:Funstuff4fun|Funstuff4fun]] ([[User talk:Funstuff4fun|talk]]) 06:12, 4 April 2026 (UTC)

Sorry, new to posting; sorry if I am misunderstanding. The text describes −0.00000000000000044 as a very small negative number. Is this saying that it is close to zero? If so, would that be better expressed as large, rather than small? [[User:Flickerwit|Flickerwit]] ([[User talk:Flickerwit|talk]]) 15:54, 4 April 2026 (UTC)
:The value is very small. The representation of the number is large (or ''fairly'' large, by some certain limited measure). But you wouldn't call 0.9 "smaller", or 'closer to zero'/"0", than "0.8888888888..." under most usages. Even though that might be correct in a string-handling context. [[Special:Contributions/81.179.199.253|81.179.199.253]] 19:32, 4 April 2026 (UTC)
:"Greater" and "lesser" work like that (with -1 being greater than -2), but "larger" and "smaller" are more ambiguous, and often refer to the absolute value. [[Special:Contributions/192.112.253.21|192.112.253.21]] 02:58, 6 April 2026 (UTC)
::One generally would not describe −0.00000000000000044 as "large" (rather than "larger", in direct comparison), except maybe in the implicit context of numbers that routinely are orders of magnitude less (in absolute terms) ''or'' are consistently more negative (e.g. zero is an ''upper'' limit and one or other of -0.5, -5 or -5,000,000 could be more typical value).
::In the context of natural numbers, it is "small" in the grand scheme of things (or 'extremely middling', on a signum-observing basis, given how close to zero it is), especially given the implied floating precision which might suggest that 44,000,000,000,000,000 (or something not too disimilar to it — same {{w|significand}}, as above, but the most positive version of the base-exponent, not the nost negative) is another possible stored value that can be represented. [[Special:Contributions/82.132.239.70|82.132.239.70]] 12:58, 6 April 2026 (UTC)

Considering how close to April Fools this comic is, it could be a remnant of such a prank that they haven't bothered to clean up yet. [[Special:Contributions/2001:1C02:1A9D:9700:A420:F4F:966C:167E|2001:1C02:1A9D:9700:A420:F4F:966C:167E]] 16:32, 4 April 2026 (UTC)

If anyone's wondering, it appears that they made it roughly 5,879 millennia, six centuries, and one decade without an integer overflow error. [[User:DL Draco Rex|DL Draco Rex]] ([[User talk:DL Draco Rex|talk]]) 19:34, 5 April 2026 (UTC)
:...I rather think it means that it will be that long until they ''aren't'' having one. ;) [[Special:Contributions/81.179.199.253|81.179.199.253]] 21:08, 5 April 2026 (UTC)

I don't think it's significant that Cueball appears to be floating. Randall sometimes draws people in chairs that way. See, for example, [[2949]], [[3015]], and [[3052]]. —[[User:Scs|Scs]] ([[User talk:Scs|talk]]) 23:25, 5 April 2026 (UTC)
:Some of the examples are also seen in What If? and What If? 2. (Yup) [[User:Cream Starlight|Cream Starlight]] ([[User talk:Cream Starlight|talk]]) 04:42, 6 April 2026 (UTC)

I agree with [[User:DL Draco Rex|DL Draco Rex]]: they started a 32 bit signed integer counter on -5877585-09-23 of the [https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar# proleptic Gregorian calendar], so that the counter goes

{| class="wikitable"
|+ days since our last integer overflow.
|-
! counter !! date
|-
| 0 || -5877585-09-23
|-
| 1 || -5877585-09-24
|-
| 2 || -5877585-09-25
|-
| ... || ...
|-
| 2146743572 || -001-12-30
|-
| 2146743573 || -001-12-31
|-
| 2146743574 || 0000-01-01
|-
| 2146743575 || 0000-01-02
|-
| ... || ...
|-
| 2147483646 || 2026-04-01
|-
| 2147483647 || 2026-04-02
|-
| -2147483648 || 2026-04-03
|}

[[User:Qprz|Qprz]] ([[User talk:Qprz|talk]]) 12:59, 6 April 2026 (UTC)

<Skeletor Voice>Remember! When a company celebrates 365 days since an incident, they are celebrating the anniversary of said incident. ...Until we meet again!</Skeletor Voice> [[Special:Contributions/57.140.28.54|57.140.28.54]] 13:57, 6 April 2026 (UTC)

BTW there is an off-by-one error in the sentence

:2,147,483,647 days from the comic's date of publication (April 3rd, 2026) is approximately October 12th of the year 5,881,636.

According to numpy datetime64 we have

<pre>
>>> np.datetime64('2026-04-03', 'D') + 2147483647
np.datetime64('5881636-10-11')
</pre>

so I would rather say "2,147,483,647 days from the comic's date of publication (April 3rd, 2026) is October ''11th'' of the year 5,881,636 of the Gregorian calendar".

The computation above is exact with respect of the Gregorian calendar rules, not approximate.
Concerns about changes in the length of day (LOD) due to [[https://en.wikipedia.org/wiki/Tidal_acceleration tidal braking]] are not relevant here, since the Gregorian Calendar counts days, irrespective of their measured length in SI seconds. What matters is the discrepancy between the mean Gregorian year with respect to mean tropical year, which is also slowly changing. This discrepancy will require a calendar reform if the vernal equinox is to be kept close to the current date (March 21), in about 1200 years, see [[https://en.wikipedia.org/wiki/Tropical_year#Calendar_year Calendar Year]]. But the Gregorian Calendar is strictly algoritmical, not observational, so its extrapolation in a distant future is legitimate.

[[User:Qprz|Qprz]] ([[User talk:Qprz|talk]]) 14:20, 6 April 2026 (UTC)

What is the source of the claim that the original version of the comic has -0.0[...]017? If anyone has a copy of that version, it belongs in a "Trivia" section. Until then, extraordinary claims require extraordinary evidence... [[User:Eunakria|Eunakria]] ([[User talk:Eunakria|talk]]) 22:39, 6 April 2026 (UTC)

Rob

2024-10-09T14:10:47Z

Eunakria: Revert [https://www.explainxkcd.com/wiki/index.php?title=Rob&oldid=87248 this] ancient edit. The scare quotes are unnecessary and the subtext is not explained or apparent. Feel free to add them back with explanation

{{Infobox character
| image = Rob.png
| imagesize = 200px
| caption = '
| first_appearance = [[276: Fixed Width]]
}}

<noinclude>:''For a list of comics, see [[:Category:Comics featuring Rob|Comics featuring Rob]].''
:''For the generic Rob, see [[Cueball]].''</noinclude>

'''Rob''' is a [[stick figure]] character in [[xkcd]]. Rob has no identifying features and is a [[Cueball]]. In most cases, he seems to represent the same character, usually being portrayed as [[Black Hat]]'s roommate. He is one of the few of Randall's characters to be given a name. In [[276: Fixed Width]], his screen name appears as "rob", and in [[723: Seismic Waves]] he is posting on the internet as "robm163". In [[838: Incident]] his username appears as "robm". In [[1783: Emails]], Cueball replies to his email in the title text.

After the Emails comic, Rob is not mentioned for 800 comics before the name is used in [[2584: Headline Words]]. Cueball is also in this comic, but it seems like Cueball represents Randall rather than Rob in the comic.

==Relationships==
Rob had a relationship with a woman known as <emily> on IM. This ended tragically in [[276: Fixed Width]] when he told her the relationship was only for sex while he wasn't really paying attention to what he was writing; he just wanted their chat responses to line up nicely on the screen. Two years later, in 2009, he had a relationship of a few months with what ended up being a spam bot. He discovered this when he asked the bot to pass what it calls a VK test, a reference to the world of Blade Runner, where they use a Voight-Kampff (VK) test to help determine if someone is a replicant. This happened in [[632: Suspicion]].

In [[647: Scary]] we find that he has a nephew born after September 11, 2001, but by 2009 he was old enough to have discussions with Rob about it.

In [[1102: Fastest-Growing]] it seems that Rob is [[Black Hat|Black Hat's]] roommate. In fact, it's possible that within the xkcd continuity, every time we see Black Hat's roommate, it's Rob. But with no name mentioned it is not enough to list these comics as comics featuring Rob.

{{navbox-characters}}
[[Category:Characters]]
[[Category:Minor characters]]

2989: Physics Lab Thermostat

2024-09-25T04:54:54Z

Eunakria: Undo revision 351117 by 172.70.211.84 (talk). There's no need to antagonize the other editors.

{{comic
| number = 2989
| date = September 23, 2024
| title = Physics Lab Thermostat
| image = physics_lab_thermostat_2x.png
| imagesize = 264x296px
| noexpand = true
| titletext = Hopefully the HVAC people set it to only affect the AIR in the room.
}}

==Explanation==
{{incomplete|Created by a BOLTZMANN BRAIN - Given the calculations mentioned in the comment, it would seem that the thermostat works normally in the way that turning it clockwise will increase the temperature. This should be mentioned and some kind of calculation like the one mentioned in comments section could be added for clarity/reference. Do NOT delete this tag too soon.}}

A thermostat is often used to regulate the operation of heating and/or cooling for a room. This may take the form of a simple dial, graduated by desired temperature values marked Celsius or Fahrenheit, depending upon {{w|Fahrenheit#Usage|location}}. Typically a person is expected to know what sort of temperature they will find comfortable, to have heating/cooling effects kick in as the wall-device detects a temperature more than a certain amount below/above that ideal. The basic design of a physical wall-mounted dial might relate the relative position of the dial against the current state of a {{w|Bimetallic strip#Thermostats|bimetallic coil}}, switching {{w|Bang–bang control|on or off}} the relevant systems once conditions locally drift away from the chosen ideal.

In this comic, the thermostat is installed in a physics lab, with those that work there clearly being expected to be familiar with the {{w|Boltzmann constant}}, a more fundamental method of measuring temperature which relates the average kinetic energy of a particle in a gas with the temperature of that gas. The Boltzmann constant is defined as 1.380649 × 10-23 J/K (joules per kelvin), a value that's used in the definition of {{w|SI base units}}.

Thus Randall imagines a physics lab having a dial that can alter the constant between 1.418 x 10-23 J/K and 1.351 x 10-23 J/K. If the average kinetic energy of gas particles remains constant when moving the dial, then changing the Boltzmann constant would change how this average energy is measured in {{w|kelvin}} (and therefore {{w|Conversion of scales of temperature#Comparison of temperature scales|any other measure}} of temperature), thus "changing the temperature". The equation is E=''k''T where ''k'' is the Boltzmann constant. Notice that if E is the same, lowering ''k'' implies a raised T, so the thermostat 'works' as intended. The effective range of the thermostat, presuming it is set to "room temperature" of 23°C (73°F), runs from 15°C to 29°C (59°F to 85°F), with the dial currently set for about 24°C (75°F).

You can build this "thermostat" in real life and use it to "control the temperature" of the room, even if you just craft it out of two pieces of cardboard. Assume you want a nice and warm room temperature of 300 K (about 27°C or 80°F). Rather than controlling the nature of the airflow into the lab (or convection heaters/coolers around it), or indeed having any effect on anything, it sets the definition of "1 kelvin" to a value between "each degree of freedom of every molecule has on average 1.418 x 10-23 J" and "each degree of freedom of every molecule has on average 1.351 x 10-23 J" that would correspond to the current warmth in the room being 300 K. With less energy needed for each kelvin, you have more of them. 

There have previously been control panels for properties of the universe in [[1620: Christmas Settings]] and [[1763: Catcalling]].

Because the Boltzmann constant is primarily concerned with the nature of temperature within a gas, the title text expresses concern that it might not only be applied to the air (hence the capital letters) in the room. Aside from the possibility that those responsible for the {{w|heating, ventilation, and air conditioning}} (HVAC) of the room could perhaps directly enhance or suppress the temperature in all the solids and liquids within the room, in unknown and not necessarily conducive ways, there may also be a secondary joke in which {{w|high voltage}} forms of {{w|alternating current}} (also referred to as HVAC) are influenced, in the related but distinct use of the measure for '{{w|Boltzmann constant#Thermal voltage|thermal voltage}}'.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[A black circular dial is shown with a white indicator line at the upper right. The label above the dial, enclosed in a rectangular box, says:]
:Local Boltzmann Constant
:[The two extremes of the dial are labeled as follows, the first value on the left and the second value on the right:]
:1.418×10-23 J/K
:1.351×10-23 J/K
:[The indicator line is pointing to a position on the dial somewhere around 1.375×10-23 J/K (between the 12th and 13th large ticks clockwise out of 19 total).]
:[Caption below the panel:]
:Physics Lab Thermostat

{{comic discussion}}

[[Category:Physics]]

Talk:2948: Electric vs Gas

2024-06-19T17:50:01Z

Eunakria: Reply to IP user

Now I'm not a fan of gas engines, but that argument is in bad faith. Gas engines have one ''very big'' advantage over electrics: Energy density, and by extension, range. Batteries can't come close to the energy density of hydrocarbons, despite the latters' overall lower efficiency. --[[User:Coconut Galaxy|Coconut Galaxy]] ([[User talk:Coconut Galaxy|talk]]) 17:22, 19 June 2024 (UTC)

:I think that's one of the main arguments for hybrid systems. Using a gas engine to charge an electric motor, and then using the electric motor to actually power the appliance, enables significant efficiency gains. If anything, combining the technologies enables even greater ''usable'' energy density from hydrocarbons. Hybrid electric vehicles for example are extremely efficient. [[User:Eunakria|Eunakria]] ([[User talk:Eunakria|talk]]) 17:43, 19 June 2024 (UTC)

On the other other hand, in a lot of cases an electric motor is just a gas engine with extra steps due to the current state of the power grid. [[Special:Contributions/172.68.174.232|172.68.174.232]] 17:24, 19 June 2024 (UTC)

:I'd say an electric motor powered by a hydrocarbon grid still usually makes better use of gas than a typical gas engine. Gas engines that don't always run at full throttle (as in, a gas engine in an appliance) have dramatically worse efficiency than electric motors that don't always run at full throttle. It depends ''very'' heavily on use case, though; always take measurements and run the numbers before coming to a specific conclusion. Science would be nothing without empirical data. [[User:Eunakria|Eunakria]] ([[User talk:Eunakria|talk]]) 17:50, 19 June 2024 (UTC)

Should this have [[:Category:Climate change]]? I can’t decide. [[User:Usb-rave|Usb-rave]] ([[User talk:Usb-rave|talk]]) 17:40, 19 June 2024 (UTC)

Talk:2948: Electric vs Gas

2024-06-19T17:43:49Z

Eunakria: Reply to User:Coconut Galaxy

Now I'm not a fan of gas engines, but that argument is in bad faith. Gas engines have one ''very big'' advantage over electrics: Energy density, and by extension, range. Batteries can't come close to the energy density of hydrocarbons, despite the latters' overall lower efficiency. --[[User:Coconut Galaxy|Coconut Galaxy]] ([[User talk:Coconut Galaxy|talk]]) 17:22, 19 June 2024 (UTC)

:I think that's one of the main arguments for hybrid systems. Using a gas engine to charge an electric motor, and then using the electric motor to actually power the appliance, enables significant efficiency gains. If anything, combining the technologies enables even greater ''usable'' energy density from hydrocarbons. Hybrid electric vehicles for example are extremely efficient. [[User:Eunakria|Eunakria]] ([[User talk:Eunakria|talk]]) 17:43, 19 June 2024 (UTC)

On the other other hand, in a lot of cases an electric motor is just a gas engine with extra steps due to the current state of the power grid. [[Special:Contributions/172.68.174.232|172.68.174.232]] 17:24, 19 June 2024 (UTC)

Should this have [[:Category:Climate change]]? I can’t decide. [[User:Usb-rave|Usb-rave]] ([[User talk:Usb-rave|talk]]) 17:40, 19 June 2024 (UTC)

440: Road Rage

2022-05-11T18:03:48Z

Eunakria: Undo revision 265921 by 👖🔥 (talk)

{{comic
| number = 440
| date = June 23, 2008
| title = Road Rage
| image = road rage.png
| titletext = Okay, now just as the loss hits him, slam on the brakes.
}}

==Explanation==
[[Black Hat]] is driving a car, and [[Danish]] is with him in the passenger's seat. Black Hat gets annoyed because the car behind him is "{{w|tailgating}}" (in this context, the term means that the other car is following too close to the back bumper of Black Hat's car).

Danish decides to fight back, so she turns on her laptop and finds that the car behind them also has a laptop running. Since the cars are so close, the other laptop is well within WiFi range, so she manages to establish a WiFi connection with the laptop in the other car. Then, Danish finds a security hole (in the comic, a "remote exploit"). She uses it to break into the laptop and install a speech synthesizer.
This means that the laptop in the car behind just starts saying words at Danish's will.

The driver of the other car is puzzled when he starts hearing a voice. He's completely clueless about where the voice comes from. Also, he's driving alone, so he's probably frightened (or nervous at least) to find that someone is speaking inside his car. The fact that the voice says "she'd be alive if it weren't for you" surely won't help him relax. The "shot in the dark" is the gamble that this statement is especially meaningful and poignant to the driver. As the driver is prone to tailgating, it seems likely that he could have caused a car accident—possibly a fatal one—in the past.

In the title text, Danish is continuing her revenge, asking Black Hat to slam on the brakes. Hitting the brakes is a common (though highly unsafe) way to get revenge on tailgaters. At minimum, it forces them to abruptly decelerate and hopefully frighten them, but the danger is that they don't have room to stop in time and cause a collision. The joke is that, having already achieved a complicated and psychologically painful form of revenge, Danish wants to follow it up with a much more conventional form, at the worst possible time. Since the blame for such types of accident is always given to the driver of the car behind, and since we know Black Hat is a sadistic bastard, Black Hat will no doubt enjoy adding both the blame and the traffic accident on top of what Danish has already accomplished. This may seem ironic, as Black Hat and Danish would be risking having their own car struck, but they would no doubt rather make an example than avoid the accident.

==Transcript==
:[Black Hat is driving, and Danish, who seems to be his equal, is in the passenger's seat. They are closely followed by some other vehicle.]
:Black Hat: That guy's tailgating me.
:Danish: I'll take a look.

:[A car is shown to be closely behind Black Hat's car.]
:Danish: His laptop's running, probably in the back seat. And... yup, the WiFi autoconnects.

:[Close-up of Danish using a laptop.]
:Danish: Now we just scan for remote exploits... install speech synth... And take a shot in the psychological dark.

:[Cueball's car.]
:Laptop: Hello.
:Cueball: What? Who's there?
:Laptop: She'd be alive if it weren't for you.
:Cueball: ...Oh God.

==Trivia==
This may be a continuation of [[433: Journal 5]], with Black Hat taking Danish to the "date" that was mentioned.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Danish]]

2161: An Apple a Day

2022-05-11T18:01:30Z

Eunakria: Undo revision 265667 by 👖🔥 (talk)

{{comic
| number = 2161
| date = June 10, 2019
| title = An Apple a Day
| image = an_apple_a_day.png
| titletext = Even the powerful, tart Granny Smith cultivar is proving ineffective against new Gran-negative doctors.
}}

==Explanation==
"{{w|An apple a day keeps the doctor away}}" is a common English {{w|proverb}} and {{w|rhyme}}. The suggestion is that eating one apple daily will keep you healthy, and therefore reduce your necessity to go to the doctor or, more literally, to {{w|house_call|have the doctor come to you}} as was likely the case when this proverb was first used.

[[Megan]] is giving a talk, starting with the common proverb, before continuing with "At least, it used to." In a normal scenario, this might have been to imply that eating apples is no longer enough to stay healthy. However, in this comic, this expression is reinterpreted to mean that an apple used to repel a doctor. It also suggests that keeping doctors away is of great importance, presumably because doctors in this scenario are undesirable. The method of action of apples is not specified; they could act as repellents, analogous to {{w|insect repellent}}, or possibly as lethal agents, as {{w|antibiotics}} are to {{w|bacteria}}, or {{w|fungicide|fungicides}} are to {{w|fungus|fungi}}.

Megan continues with her reinterpretation, mentioning that doctors have become resistant to apples so two or even three may be needed. As control agents become more widely used, organisms which are less sensitive to the control may become more common, as is happening with [https://www.nature.com/news/2010/100503/full/news.2010.216.html mosquitoes becoming insensitive to repellents], or {{w|antimicrobial resistance}}, and {{w|pesticide resistance}}. Such resistant organisms may require higher doses, or use of multiple control agents.

In the worst cases, doctors have become completely immune to apples (i.e., {{w|superbugs}}). A poster behind Megan shows [[:Category:Doctor Ponytail|Doctor Ponytail]] with three apples above her. Megan advocates using the 'finest' apples only in these cases (a reference to {{w|Multiple drug resistance|multidrug-resistant}} {{w|pathogens}}, where some antibiotics are only used as a last-resort to reduce the development of resistance to them).

This comic is a clear reference to the {{w|Antibiotic misuse|overuse of antibiotics}} in modern society, leading to an increase in {{w|antimicrobial resistance}} ("Superbugs"), which has seen increasing awareness in the last few years. The {{w|World Health Organization}} had the first [https://antibioticawareness.ca Antibiotic Awareness Week] in 2015, where a talk similar to the one in the comic would seem appropriate. Similar problems occur in growing plants, where various pests (whether insect, fungi, microbes, or plants) adapt to control measures, making control less effective.

In the title text, this is taken further: "Gran-negative" is a pun on {{w|Gram-negative}}, a category of bacteria. A well-known technique called {{w|Gram staining}} distinguishes two classes of bacteria (Gram positive versus Gram negative) on the basis of properties of their cell walls. In this case, Granny Smith apples are supposedly effective against Gran-positive doctors (since the name begins with "Gran"), making them ineffective against new Gran-negative doctors.

{{w|Honeycrisp}} and {{w|Granny Smith}} are two different cultivars of apples. Granny Smith apples are a refreshingly tart green apple, which have mixed reviews among apple eaters. Conversely, Honeycrisp are a very sweet apple, considered by some to be "an ideal apple for eating raw", and is the state fruit of Minnesota.

==Transcript==
:[Megan is facing straight out of a slim panel as she stands behind a lectern addressing the reader.]
:Megan: An apple a day keeps the doctor away.
:Megan: Or at least, it used to.

:[The comic zooms out revealing that Megan and the lectern are standing on a podium. Megan is pointing behind her, with a stick, to at a poster prominently featuring Doctor Ponytail with three apples over her head.]
:Megan: Over time, some doctors have developed a resistance to apples. Keeping them away takes two or three apples instead of one.
:Megan: And there are worrying signs that a few doctors may have become completely immune.

:[The comic zooms in again on Megan behind the lectern.]
:Megan: So we must stockpile our finest apples in reserve, using them to fend off only the very worst doctors.
:Megan: Honeycrisps still work on most of them, but we don't know for how long.

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]] 
[[Category:Doctor Ponytail]]
[[Category:Biology]]
[[Category:Food]]
[[Category:Public speaking]]