Explain xkcd: It's 'cause you're dumb.
In computer systems, time is measured starting from some arbitrarily chosen point. That particular time is known as the "epoch" for that system.
The UNIX operating system internally uses an epoch of January 1st, 1970, and measures time as a number of seconds from then. Since this was intended only for things internal to the OS (File last modified times and the like), using 1-Jan-1970 was safe as no UNIX systems existed before that date. However, since UNIX included a number of system functions to manipulate these dates, some developers mistook them for a general purpose date object, and misused them in applications requiring dates before the epoch. Such usage would inevitably fail (for example, the date might be considered to be far in the future, instead of in the past)
In the comic, one developer has clearly misused the system date in this way, and the second developer is making a pun by combining "Epoch" with "Epic Fail" - a colloquial term meaning "a very big mistake was made".
- [Cueball sits at a computer, staring at the screen and rubbing his chin in thought. A friend stands behind him]
- Cueball: Weird - My code's crashing when given pre-1970 dates.
- Friend [pointing at the computer]: Epoch fail!
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That is why on Unix epoch (the time_t type) is signed type, and covers dates before epoch. --JakubNarebski (talk) 19:52, 5 July 2013 (UTC)
- Ohh, and much more is missing. I did mark it as incomplete. We also have to talk about the time frame the 32bit epoch does cover, and what would be changed by using a 64bit variable. What will happen on 19 January 2038?--Dgbrt (talk) 20:17, 5 July 2013 (UTC)
- The general hope, it appears, is that 64-bit integers will be firmly in place, having ousted the feeble 32-bit integers from the system time. As has been demonstrated in innumerable instances, it's rather difficult to eliminate legacy code from systems due to attempts to support older systems in a backward-compatible methodology. In short, however, it will take time to resolve time. Thokling (talk) 05:34, 22 September 2013 (UTC)
- I so look forward to seeing Epoch boom to hurriedly uplift 32 bit code before the 'end'. Similar to the Y2K boom. I might consider lending my expertise at a considerable markup. :) Puck0687 (talk) 17:57, 4 December 2015 (UTC)
- Rewrite needed
The current explanation barely has to do with the actual topic of the comic. Instead it explains several unrelated qualities of Unix time, and petty much skips over the actual epoch thing. Needs a rewrite.
--NeatNit 18.104.22.168 05:59, 8 February 2015 (UTC)
Why would anyone want to take the square root of a timestamp? It is much more likely that Cueballs program just handles negative time values incorrectly. Condor70 (talk) 07:15, 14 November 2016 (UTC)