2012/7/11 phasis68 (Heesob Park) <phasis / gmail.com>:
>
> I found some discrepancy between DateTime#strftime('%s') and Time#strftime('%s') on date before 1582-10-15

This is not a bug.

The difference is caused because
Time uses Proleptic Gregorian calendar (doc/NEWS-1.9.2) but
DateTime uses Julian/Gregorian calendar at Italy by default.

I guess you can use DateTime with Proleptic Gregorian calendar (doc/NEWS-1.9.3).
-- 
Tanaka Akira