js> d = new Date('1/1/1999 12:30 AM') Fri Jan 01 12:30:00 PST 1999 js> d = new Date('1/1/1999 12:30 PM') Sat Jan 02 00:30:00 PST 1999 ... This also occurs in our Java implementation. Looks like I copied the parsing code a little too faithfully.

Checked in a fix to the tip, SpiderMonkeyDev_BRANCH, SpiderMonkey140_BRANCH, and the java implementation. The fix checks for 12:XX AM (subtract 12 for this case, otherwise do nothing for AM) and checks for 12:XX PM (subtract 12 for any hour except 12; leave 12:XX PM alone.) This fix also applies the hour <= 12 check to the AM case that previously only applied to the PM case (because no time adjustment was done for AM.) This means that the date string '1/1/1999 13:30 AM' no longer produces a valid date. I'm guessing that this will be ok, because '1/1/1999 13:30 PM' never did. Old behavior: js> d = new Date('1/1/1999 13:30 AM') Fri Jan 01 13:30:00 GMT-0800 (PST) 1999 js> d = new Date('1/1/1999 13:30 PM') Invalid Date js> d = new Date('1/1/1999 12:30 AM') Fri Jan 01 12:30:00 GMT-0800 (PST) 1999 js> d = new Date('1/1/1999 12:30 PM') Sat Jan 02 00:30:00 GMT-0800 (PST) 1999 New behavior: js> d = new Date('1/1/1999 13:30 AM') Invalid Date js> d = new Date('1/1/1999 13:30 PM') Invalid Date js> d = new Date('1/1/1999 12:30 AM') Fri Jan 01 00:30:00 GMT-0800 (PST) 1999 js> d = new Date('1/1/1999 12:30 PM') Fri Jan 01 12:30:00 GMT-0800 (PST) 1999

Checked in a fix to the tip, SpiderMonkeyDev_BRANCH, SpiderMonkey140_BRANCH, and the java implementation. The fix checks for 12:XX AM (subtract 12 for this case, otherwise do nothing for AM) and checks for 12:XX PM (subtract 12 for any hour except 12; leave 12:XX PM alone.) This fix also applies the hour <= 12 check to the AM case that previously only applied to the PM case (because no time adjustment was done for AM.) This means that the date string '1/1/1999 13:30 AM' no longer produces a valid date. I'm guessing that this will be ok, because '1/1/1999 13:30 PM' never did. Old behavior: js> d = new Date('1/1/1999 13:30 AM') Fri Jan 01 13:30:00 GMT-0800 (PST) 1999 js> d = new Date('1/1/1999 13:30 PM') Invalid Date js> d = new Date('1/1/1999 12:30 AM') Fri Jan 01 12:30:00 GMT-0800 (PST) 1999 js> d = new Date('1/1/1999 12:30 PM') Sat Jan 02 00:30:00 GMT-0800 (PST) 1999 New behavior: js> d = new Date('1/1/1999 13:30 AM') Invalid Date js> d = new Date('1/1/1999 13:30 PM') Invalid Date js> d = new Date('1/1/1999 12:30 AM') Fri Jan 01 00:30:00 GMT-0800 (PST) 1999 js> d = new Date('1/1/1999 12:30 PM') Fri Jan 01 12:30:00 GMT-0800 (PST) 1999

so are you going to write some test cases for Date.parse. :)

Changing component to "Javascript Engine". "Javascript" component is being retired.

checked in a regression test: mozilla/js/tests/ecma/Date/15.9.4.2-1.js