r"
^\s*
(?:
(?P<date>
(?:[\[<\(]\s*)? # opening bracket
(?:
# date time
(?:
# date
(?:
(?: # matches mm-dd-yyyy mm-dd-yy mm-dd
\d{1,2}-\d{1,2}
(?:
-
(?:\d{4}|\d{2})
)?
)
|
(?: # matches mm/dd/yyyy mm/dd/yy mm/dd
\d{1,2}\/\d{1,2}
(?:
\/
(?:\d{4}|\d{2})
)?