Macintosh Y2020
Basal Gangster (via Keith Kaisershot, Hacker News):
Macintosh clock time expires at 06:28:16 GMT Monday February 6, 2040. That’s going to be a problem for users of the old Macintosh, but it is a problem for 20 years from now. Fixing that will be possible, but it will require some deeper cutting than we need to do now. The problem now is just setting the clock.
[…]
When the clock struck Midnight on Jan 1 the clocks in most old Macintoshes just ticked right on into 2020, the correct date continued to be shown in the control panel and on any files created or changed. Many retro-computing hobbyists and other who use the old machines may not know there is any problem, until they try to set the date in the Alarm Clock or Date & Time control panel.
[…]
Any value between 20 and 99 results in a 20th century date. Entries between 00 and 19 (inclusive), gives 21st century results. This is the problem being encountered by users now. It is like the Y2k bug, except that Apple windowed years into the range 1920-2019 instead of 1900-1999.
[…]
Just change 20 ($14) in the comparison to 40 ($28), and 2-digit years will be interpreted as being between 1939 and 2040. I can try and test this patch in TMON, but any change in TMON is applied to the program in memory, not in the code on disk, and it will not stick. It is necessary to change the Control Panel code on disk.
And for those who aren't aware, this is a good time to familiarize yourself with the Year 2038 problem. (When the Unix time clock exceeds the value of a 32-bit integer.)
https://en.wikipedia.org/wiki/Year_2038_problem