Reproducing the bug inside the IRB:

Time.strptime("1", "%s")
=> 2011-10-03 15:51:02 -0700

as opposed to:

Date.strptime("1", "%s").to_time
=> 1970-01-01 00:00:00 -0800

The docs read that Time.strptime relies on Date._strptime to do the parsing, and then converts it to a Time object. Date._strptime returns the time only as seconds (with "%s" as the format string):

Date.send(:_strptime, "100000", "%s")
=> {:seconds=>100000}

Class Date seems to check for this case (see Date.rewrite_frags) but class Time does not; Time seems to assume that Date._strptime will return a hash with all of the key/values necessary to correctly call Time.make_time:

File lib/time.rb, line 277¶

d = Date._strptime(date, format)
. . .
make_time(year, d[:mon], d[:mday], d[:hour], d[:min], d[:sec], d[:sec_fraction], d[:zone], now)