Year 2038 bug

What is the year 2038 bug?

In the first month of the year 2038 C.E. many computers will encounter a date-related bug in their operating systems and/or in the applications they run. This can result in incorrect and grossly inaccurate dates being reported by the operating system and/or applications. The effect of this bug is hard to predict, because many applications are not prepared for the resulting "skip" in reported time - anywhere from 1901 to a "broken record" repeat of the reported time at the second the bug occurs. Also, leap seconds may make some small adjustment to the actual time the bug expresses itself. I expect this bug to cause serious problems on many platforms, especially Unix and Unix-like platforms, because these systems will "run out of time". Starting at GMT 03:14:07, Tuesday, January 19, 2038, expect to see lots of systems around the world breaking magnificently: satellites falling out of orbit, massive power outages (like the 2003 North American blackout), hospital life support system failures, phone system interruptions (including 911 emergency services), banking system crashes, etc. One second after this critical second, many of these systems will have wildly inaccurate date settings, producing all kinds of unpredictable consequences. In short, many of the dire predictions for the year 2000 are much more likely to actually occur in the year 2038! Consider the year 2000 just a dry run. In case you think we can sit on this issue for another 30 years before addressing it, consider that reports of temporal echoes of the 2038 problem are already starting to appear in future date calculations for mortgages and vital statistics!.

What causes it?

What makes January 19, 2038 a special day? Unix and Unix-like operating systems do not calculate time in the Gregorian calendar, they simply count time in seconds since their arbitrary "birthday", GMT 00:00:00, Thursday, January 1, 1970 C.E. The industry-wide practice is to use a 32-bit variable for this number (32-bit signed time_t). Imagine an odometer with 32 wheels, each marked to count from 0 and 1 (for base-2 counting), with the end wheel used to indicate a positive or negative integer. The largest possible value for this integer is 2**31-1 = 2,147,483,647 (over two billion). 2,147,483,647 seconds after Unix's birthday corresponds to GMT 03:14:07, Tuesday, January 19, 2038. One second later, many Unix systems will revert to their birth date (like an odometer rollover from 999999 to 000000). Because the end bit indicating positive/negative integer may flip over, some systems may revert the date to 20:45:52, Friday, December 13, 1901 (which corresponds to GMT 00:00:00 Thursday, January 1, 1970 minus 2**31 seconds). Hence the media may nickname this the "Friday the Thirteenth Bug".



Sources:

http://en.wikipedia.org/wiki/Year_2038_problem

http://www.2038bug.com/

http://computer.howstuffworks.com/question75.htm