Title text: Someday, some big historical event will happen during the DST changeover, and all the tick-tock articles chronicling how it unfolded will have to include a really annoying explanation next to their timelines.
In this comic Black Hat is a supervillain, befitting his character. He plans to use drones and explosives to move the entire State of California into the Pacific, a la Lex Luthor in the 1978 Superman movie.
His henchmen are Cueball and Megan. The latter appears to be a programmer who is concerned that the mission (and hence the drones' coding) may have to account for time/date adjustments, such as time zones and daylight saving time (DST), which would be a factor if the event took place on the wrong date or the landmasses were pushed too far apart. (Though by coding the drones on UTC, the drones would not need to change time zones, except for displaying the local time for some reason, which would likely be unneeded.)
In computer programming, working with dates and times can be complicated. Think about leap years or leap seconds, the non existing year zero which even worse for scientists does exist in astronomical calendars, or the Y2K and year 2038 problem. Nevertheless in this comic there is only a time zone problem mentioned. To handle this the tz database, also known as tzdata, provides all relevant information for every country back to 1970 and, less accurate, before. But it's still up to the programmer to use this data in useful ways.
Supervillains have reason to fear daylight saving time issues. In 1999, two coordinated car bombings ended up killing the terrorists transporting the bombs when they exploded one hour early. Details explained e.g. on the Darwin Awards site.
Time zones and DST can give seemingly nonsensical results when used improperly. For example, a flight going west might leave at 02:00pm and reach its destination at 03:00pm while the reverse flight will leave at 02:00pm and arrive at 05:00pm. In both cases, the travel time is two hours, but the one hour difference between the two time zones makes it seem otherwise. You might even find yourself arriving at your destination at an earlier time than your departure! DST can also makes a given time mean two different things, if after 01:59am you go back to 01:00 am, 01:30am can either be one hour after 00:30am, or one hour before 02:30am. Or in the reverse change, some dates don't actually exist, like 02:30 when going straight from 01:59 to 03:00. Humans often avoid this issue by being in only one place at the same time, or by sleeping when the DST changes happen, but computer communications often span over large distances, and drones don't need to sleep at night. Megan wants to make sure she won't have to deal with the difficult problem of communication between drones and other systems with those issues, where a single poorly communicated date can have disastrous effects (although possibly far less disastrous than moving California into the sea).
California is currently located entirely within the UTC-8 time zone (at standard time PST, while in summer PDT is at UTC-7). But after Black Hat's actions California is at risk of floating West into the next time zone at UTC-9.
However, in reality, time zones in the United States are determined by Department of Transportation regulations, and California's time zone is not defined based on its longitude. Consequently, even if California were pushed out to sea, its time zone would remain the same unless the Department of Transportation issued a regulation otherwise, so Megan can rest easy. (On the other hand, Black Hat could alter the time zone of any of the East Coast states except Maine if his drones could push the state east of 67°30″ W. longitude, since the Eastern Time Zone's eastern boundary is mostly based on longitude, except for Maine.)
Note: Megan should be happy Black Hat hasn't planned to involve Arizona in his scheme.
A "tick tock article" is a term in journalism for a step by step account of an event or timeline, such as this one recounting the end of the 2011 MLB regular season. Such an article published for an event during the change to or from Daylight Saving Time would need to account for the changeover, making the timeline confusing for those unaware of the switch.
- [On the left of this single panel comic Black Hat sits on a high throne, showing a fist, and looking down to Cueball and Magan who stand in front of him on the right.]
- Black Hat: ... then, after our drones take control of the cities, we will detonate the devices. California will break off from the mainland and drift out to sea!
- Megan: How far out to sea? Will it put any of the cities in the UTC-9 time zone?
- Black Hat: What? I don't know.
- Megan: One request: Can we make sure this doesn't happen during the daylight saving changeover?
- [Caption below the panel:]
- You can tell when someone's been a programmer for a while because they develop a deep-seated fear of time zone problems.
- Different time zones often confuse people. When xkcd comics are released on Monday, Wednesday, or Friday early as possible at 00:00 according to Randall's home at Eastern Time (EST/EDT) it is still the day before in the most regions of the United States further to the west. In California (PST/PDT) that would be 21:00 in the evening before. Nevertheless most comics are released later when the entire US is at the same day. This particular comic was released at 13:00 UTC, which was 09:00 EDT or 06:00 PDT.
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California is UTC-8 during the winter, but UTC-7 during the summer. RandalSchwartz (talk) 15:16, 30 August 2017 (UTC)
- I've clarified this. --Dgbrt (talk) 16:13, 30 August 2017 (UTC)
For some reason, I can't help but to think of this Tom Scott video. I guess it represents well the feeling programers must have when talking about time zones. 188.8.131.52 16:49, 30 August 2017 (UTC)
Is it at all clear that Cueball and Megan are "henchmen"? I assumed they were captured heros that were to be put to death, but first the supervillain was confessing his evil plan to them, ala EvilGloating. JohnHawkinson (talk) 18:20, 30 August 2017 (UTC)
- I think their purely technical concerns would suggest they don't object to the plan itself, they just want to make sure it's as painless for them as possible Charith (talk) 19:38, 30 August 2017 (UTC)
- To me, the position with black hat on a throne and the people opposite him seems more like a villain gloating over his plan. But the heroes this week are programmers (who else would go up against a madman who seems to be building a drone army?) - and when they hear what he's actually planning, the time zone thing becomes their biggest concern. -- 184.108.40.206 09:50, 31 August 2017 (UTC)
- Considering that they're giving feedback, helping define (and redefine, and make requests regarding to) the plan, I feel they can only be on the same side as Black Hat. In fact, the freedom they enjoy to do this suggests to me that they're higher than henchmen or minions, that they're likely his lieutenants, being the next step down in the managment heirarchy. "Right Hand Men", as it were. The ones he can confide in, plan with. Like Bob to Joker in the first Michael Keaton Batman movie (saw it again this weekend, no wonder it's the first example to come to mind, LOL!). NiceGuy1 (talk) 05:26, 5 September 2017 (UTC)
- The phrase 'can we be sure' makes it clear that they are members of Black Hat's organisation. Or at least Megan is; Cueball could be anyone including a captured hero. Also would it be too obvious to highlight the central premise of the comic, that instead of a normal person's reaction to hearing of the dastardly plan, Megan can only fixate on the time zone issue? 220.127.116.11 (talk) (please sign your comments with ~~~~)
Also a nice one for programmers, when governments suddenly decide to change the rules: http://www.bbc.com/news/world-europe-34631326 --18.104.22.168 20:07, 30 August 2017 (UTC)
- About arizona, the article on timeanddate.com might be a better explanation. (The current link is ). 22.214.171.124 20:33, 30 August 2017 (UTC)
Fun fact: this technology can also be used by the good guys to fight the evil. We could move the tectonic plates around to precisely control Earth's moment of inertia, eliminating the need for leap seconds! --126.96.36.199 03:00, 31 August 2017 (UTC)
To whoever wrote the sentence starting with "Humans often avoid this issue": Kudos! Best sentence I read here for a very long time! Plus: something funny to read: http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time Elektrizikekswerk (talk) 07:36, 31 August 2017 (UTC)
- Thanks! 188.8.131.52 10:11, 1 September 2017 (UTC)
I also appreciate the presence of the "citation needed" in that sentence - brilliantly placed! I'm delighted that Randall has raised awareness on this issue, because it gives me a chance to bring up my latest time discovery, Amsterdam time from May, 1 1909 until July 1, 1937, which was GMT +0h 19m 32.13s (yes - to the hundredth of a second). My family visited Amsterdam this past summer, and as luck would have it we got to climb the Westertoren, giving me ample opportunity to inform the guides about its special place in timezone management hell (amusing for a church tower)! Tovodeverett (talk) 11:46, 31 August 2017 (UTC)
- I'm glad the "citation needed" is back (no I didn't add it back myself), I had two "Citation needed" in that sentence but they were removed because "not funny anymore", and I did notice that it wasn't used for many pages, so I wondered if the trope was still up to date. 184.108.40.206 10:11, 1 September 2017 (UTC)
- The "Citation needed" template was used too much in the past which some still liked and others not. But consider, it doesn't explain anything which is the main purpose of the article.--Dgbrt (talk) 12:45, 1 September 2017 (UTC)
- That's why I didn't add it back myself, I understand that some people may think it has been used too often. I've just checked "What if" to see how Randall himself is using the joke (well, with more variation than the explainxkcd version) and although he had a "citation needed" in the very last answer, there was none for fourteen pages in a row. So I guess using it lightly is best aligned with Randall's sense of humor. Which was always the goal of the  trope IMHO, not to explain, but to keep in touch with the XKCD culture. But since no joke should be left unexplained here, maybe the explanation that this trope is used as a joke on very obvious statement should be made into a more visible disclaimer on the  page. 220.127.116.11 15:18, 1 September 2017 (UTC)
- That was "Amsterdam time", the time on which the sun is at its highest point at noon in Amsterdam. Earlier in the 19th century, most cities held to their own time. In 1892, the railways decided to use _Greenwich_ time, even though more and more cities used Amsterdam time -- so the trains were always using a time 19m32.12 different from the rest of the country. Until 1909, as you note, when everybody had to switch to Amsterdam time, that mostly meant the railways. 08:21, 1 September 2017 (UTC) 18.104.22.168 (talk) (please sign your comments with ~~~~)
I was working on an application with multiple remote devices measuring temperatures. The units had internal clocks, but some units were set to change automatically with daylight savings time, some weren't, and some apparently had the wrong dates set for the switchover. They were also located in two different time zones. I would have loved to have them all set to UTC and handle the time zone conversion at the central facility. However, this wasn't really practical as parts of the network were already installed. However, it was good enough since the real need was to record trends and report when temperatures were above alarm levels. There is also a time standard that doesn't use leap seconds (TAI). (This is used for the GPS system.) I have heard a number of proposals that the timing standard for computer equipment use the time without leap seconds for recording events. http://tycho.usno.navy.mil/systime.html UTC is TAI with adjustments for leap seconds. Look at http://gpsworld.com/leap-second-implementation-confuses-some-receivers/ (There were other situations) Some systems had some calculations using UTC and some using TAI, and mistakes in consistency caused some major problems. BradleyRoss (talk) 20:46, 31 August 2017 (UTC)
I have to question this: "However, in reality, time zones in the United States are determined by Department of Transportation regulations, and California's time zone is not defined based on its longitude.". While I'm convinced it's true that this department does this, it wouldn't be able to ignore reality! Time Zones EXIST because of the sun being in different positions depending on your longitude. That 4pm sun is at 3pm position over there. If California moved far enough, the Time Zone would NEED to change, they'd have no choice! I mean, I know most of the zone borders are hardly straight, in order to to work in conjunction with other borders, but there are limits. NiceGuy1 (talk) 05:09, 5 September 2017 (UTC)
- I've been to the Maldives in March. There you have a different timezone on every island, regardless of it's possition (Mali +1, Mali +0,5...). The sun does not care much. 22.214.171.124 13:01, 5 September 2017 (UTC)Thomy
- People can and do tolerate some discrepancies between their longitude and their time zone. Look at all the places where there is a time zone change going south or north -- same longitude, different time zone. Or look at China, where the entire country is officially on Beijing time no matter how far west they go. (Except in Xinjiang, where it gets complicated.) --126.96.36.199 15:37, 11 October 2017 (UTC)