Fix multiple issues:
- Remove bogus 2038 check and add overflow checks in the appropriate places.
- Correct incomplete leap year calculation that broke things after 2100.
- Check localtime return values
- Change int calculations to time_t to avoid oveflow.
- Consistently check/return -1 and remove bogus comment about not being
able to return -1.
Now:
$ date -d 20991201
Tue Dec 1 00:00:00 EST 2099
$ date -d 40991201
Tue Dec 1 00:00:00 EST 4099
$ date -d 10000000991201
Tue Dec 1 00:00:00 EST 1000000099
TIME=0:04.48 CPU=117.8% (5.288u 0.000s) SWAPS=0 (0+95)pf (0i+0o) (0Kc+0Kd)
$ date -d 100000000991201
date: Cannot parse `100000000991201'
TIME=0:53.48 CPU=99.2% (53.086u 0.000s) SWAPS=0 (0+96)pf (0i+0o) (0Kc+0Kd)
Exit 1
49f71b9cd5