Why does localtime() return $YEAR-1900?

szabgab has asked for the wisdom of the Perl Monks concerning the following question:

field 5 returned by localtime() in list context is the year. In order to get back the date one needs to write $year + 1900.

   ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);

Does anyone know why did Larry make it that way?

Update

Title corrected thanks to Re: Why does localtime() return 1900-$YEAR?

Comment on Why does localtime() return $YEAR-1900?

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Re: Why does localtime() return 1900-$YEAR? by bart (Canon) on Jan 31, 2011 at 12:00 UTC
It's `$year-1900`, not `1900-$year`. And it's a fix for an old custom that started a long time ago (70s - 80s) when they thought "2-digit years should be enough for any date". So when 2000 came along, they had a problem. Replacing 2 digit years with years since 1900 was the easiest, backward compatible fix.	[reply] [d/l] [select]
Re^2: Why does localtime() return 1900-$YEAR? by apl (Monsignor) on Jan 31, 2011 at 12:44 UTC
Further, you need 11 bits to specify 1999, while only 7 are necessary for 99. Believe it or not, being able to to save 4 bits a record (or structure) was a big deal back in the '70s... Yes, I'm a dinosaur, as I've been programming since 1972...	[reply]
Re^3: Why does localtime() return 1900-$YEAR? by szabgab (Priest) on Jan 31, 2011 at 13:51 UTC
Perl was first released in 1987. The memory issue was much less important by that time and I am quite sure people were already aware of the bug 2000. Though that's an interesting other question. When did people start to talk about "bug 2000"?	[reply]
Re^4: Why does localtime() return 1900-$YEAR? by ikegami (Patriarch) on Jan 31, 2011 at 16:15 UTC
Re^4: Why does localtime() return 1900-$YEAR? by Utilitarian (Vicar) on Feb 01, 2011 at 09:28 UTC
Re^4: Why does localtime() return 1900-$YEAR? by apl (Monsignor) on Feb 01, 2011 at 11:11 UTC
Re: Why does localtime() return $YEAR-1900? by cdarke (Prior) on Jan 31, 2011 at 13:29 UTC
This is often called Broken-down time and is used in a C structure called struct tm. Perl is written in C, so it is not surprising that it uses it. Neither is Perl alone in that, many other languages use this format. I guess Larry used it because everyone would expect that format and is familiar with it.	[reply]
Re: Why does localtime() return 1900-$YEAR? by marto (Cardinal) on Jan 31, 2011 at 11:59 UTC
I suspect that it's based on Time.h. See Time::localtime	[reply]