Comment 2 for bug 1613709

The reference was very helpful :-) Thanks a lot
I have modified the code in Open-ILS/src/templates/opac/parts/js.tt2 (the line 10) to:

            alert ("[% l('You have entered an invalid date, or an improperly formatted date. Please enter Date of Birth in YYYY-MM-DD or YYYY/MM/DD format and try again.') %]")

and added the translation of the string to cs-CZ.po file
Now the error message is translated properly, so I think this piece of code could be used as a patch (if the patch hasn´t been created yet).

But I think I have discovered there is a wrong information in the date of birth field example and in the error message - I don´t think the YYYY/MM/DD format work: when the date of birth in the patron registration form is entered in this format, the field remain blank when the pending patron is loaded in the staff client.
I have tested this both in the Czech and the English OPAC and both in the English and the Czech staff client locale (not the web staff client) and with the original js.tt2 file (just to be sure my modification or the file is has not been the source of the problem).
The YYYY-MM-DD format is O.K.