Leap Year Date Problems
Anyone know of any good stories about leap year date problems in software. I'd be willing to bet that leap years have cause more problems in software than all of Y2K.
Lotus 123 thought 1900 was a leap year.
Also did you know that when is a leap year, there is a leap day in that year, but it's not Feb.29. but Feb.24. as I remember. Strange but true,
I thought the Feb 24th thing was a bit weird so I checked - at least in the European Union it *used* to be true. There's a bit about it on Wikipedia: http://en.wikipedia.org/wiki/Leap_year . You learn something new every day.
a cynic writes...
And two other posts seemed to have lept in while I was replying to Joel :)
"Meaning date calculations across Excel/Visual Basic boundaries are screwed up, but only for January and February 1900."
When it comes to Gantt charts used to solve real problems, Leap year comes second only to DST on the pain-in-the-butt scale.
Um, am I missing something here? Even if you call Feb 24 your leap day, you still end up with a Feb 29 only in leap years, right?
>Even if you call Feb 24 your leap day, you still end up with a Feb 29 only in leap years, right?
I suspect it had something to do with Saints' days. For some reason a gap between the Saints for the 23rd Feb and 24th Feb was considered less harmful than a gap between the 28th Feb and 1st March would have been.
The practice of inserting an extra day after February 23rd (not the 28th) goes back to the ancient Roman tradition of adding intercalary months. Before the calendar reform that gave us the Julian calendar, the lunar calendar was kept in synch with the solar year by the occasional insertion of an extra month (called Intercalaris). By royal decree, this extra month was inserted after the "seventh day before the Kalendae [i.e., the first] of March", which corresponds to our February 24th. Later, when Julius Caesar reformed the calendar, and instituted the practice of an additional day every four years, he decreed the sixth day before the Kalendae of March be doubled. This second sixth day was called bisixtiles.
If you had a child born on February 29th, what wll that child birday be after Leap year?
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