parse_date() -- and str2time(), which delegates to it -- used regexes with
ambiguous adjacent greedy runs (year/clock/timezone digits and
timezone/ASCII-timezone letters) before a trailing anchor. A valid-looking
date prefix followed by a long interior run of digits, letters, or whitespace
and a trailing junk character forced O(N^2) backtracking, so a ~100 KB string
burned tens of seconds of CPU: a denial of service.