Note that  . (dot) is a metacharacter | regex metacharacter (matching anything except a newline unless the  /s regex modifier is asserted, in which case it matches anything), so tybalt89's solution also identifies  '12x12y17' and  '09_30^2017' as dates.

You need to decide how dot is to be interpreted in your specifiers because another step seems to be needed (unless this is one of the downstream checks you envision).