string:try-parse-date
builtin-function
(string:try-parse-date str &key format culture)
Converts a string to a DateTime.
make-html > (.try-parse-date "20130104" :format "yyyyMMdd")
it: "2013-04-01"
make-html > (.try-parse-date "20139904" :format "yyyyMMdd")
it: null