leonard@bucket.UUCP (Leonard Erickson) (07/03/89)
hjg@amms4.UUCP (Harry Gross) writes: >In article <4342@druhi.ATT.COM> terrell@druhi.ATT.COM (TerrellE) writes: >>Will your software make it into the 21st century? Does it cope with the >>Gregorian calendar reform of the 16th century? > [stuff deleted] >>The Gregorian calendar reform makes every year evenly divisible by 4 a >>leap year EXCEPT for century years. Consequently there is no January 29, > ^^^^^^^ >>2000. >Um - that ought to be February :-) By the way, the proper determination >is just a wee bit more than that stated above. Specifically, a leap year >exists if: > 1) the year is divisible by 4 AND > 2) the year is NOT divisible by 400 try: leap_year := (((year mod 4) = 0) and not ((year mod 100) = 0)) or ((year mod 400) = 0) >thus, the years 1700, 1800 and 1900 were leap years, but 2000 will NOT be >a leap year, and 2100 WILL be. Exactly backwards. In 1700 *some* countries were still on the old calendar. England and it's colonies didn't switch until September 1752. If your system has 'cal', try 'cal 9 1752' for a rather interesting display! 1800 and 1900 were not leap years, even though several major packages think differently. 2000 will be and this makes life much easier for programmers. >On the other hand, does anyone really expect their software to be up and >running in the year 2100? :-) >By the same token, I expect that DOS will have been replaced by something >else by the year 2000 (perhaps DOS 9.8 :-) and Microsoft and IBM will no >doubt have fixed the problem in that release :-) Ask people about the "epochs" on PDP systems. Nobody expected those systems to be around this long either! And as I point out above, the software *isn't* broken! -- Leonard Erickson ...!tektronix!reed!percival!bucket!leonard CIS: [70465,203] "I'm all in favor of keeping dangerous weapons out of the hands of fools. Let's start with typewriters." -- Solomon Short