Hi Xavier,

Thank you for the tip.

I don't think Heads->False is needed because Position acts on lists. StringMatchQ will return an error if any element in the list myStrings is not a string. I have been using the following, which works on lists and lists of lists that may also contain data types other than strings.

Position[myStrings, _String?(StringMatchQ[#, DatePattern[{"DayShort", " ", "MonthName", " ", "Year"}]] &)]

The only problem is that the test _String? can slow it down considerably if used repeatedly. I suppose another way to do it would be to convert all of the elements of myStrings to strings using ToString as a precaution.

Gregory