regexp.md

ISODATE

^(\d{4}-((0[1-9]|1[0-2])-([0-1][1-9]|[12][0-8])|(0[13-9]|1[012])-(29|30)|(0[13578]|1[02])-31)|(\d\d(0[48]|[2468][048]|[13579][26])|(0[48]|[2468][048]|[13579][26])00)-02-29)$

Debuggex Demo