Date::Manip versions through 7.00 for Perl return corrupted dates via non-ASCII decimal digits that pass the numeric range tests in check.
The parse regexes capture year, month and day with the \d shorthand, which on a character string matches the whole Unicode decimal digit property \p{Nd} and not just [0-9]. Date::Manip::Base::check then validates the captured fields with numeric comparisons alone ($y<1 || $y>9999, $m<1 || $m>12, $d<1 || $d>$days), and _parse_check stores the numified fields ($y+0). Perl truncates a string at the first character that is not an ASCII digit, so a field whose leading characters are ASCII digits numifies to an in-range prefix and satisfies every test: a year field of three ASCII digits followed by U+0664 ARABIC-INDIC DIGIT FOUR numifies to 202, giving the year 0202, and one non-ASCII digit in the month or day field shifts those fields the same way. The hour, minute and second fields match explicit ASCII character classes (0?[0-9], [0-5][0-9]) and do not shift, though a non-ASCII digit in a fractional hour or minute field truncates the fraction.
Any caller that passes an untrusted character string to ParseDate() or Date::Manip::Date->parse() can get back a date that differs from the string it parsed, with no parse error. Where the parsed date gates logic such as an expiry check or a retention window, the shift goes unnoticed.