The javascript code for the data validation is broken if you do not specifiy the UserDateFormat in a "long" format if you do not want to use US date formats.
If you debug then the value.DateFormat passes "DMY" or the like but the switch statement expects "DayMonthYear". If you use a culture you will use the "short" format. If you specify "DayMonthYear" in the UserDateFormat on the MaskedEditExtender then it works as expected.
The offending function is:
function MaskedEditValidatorPartDate(value,mask,MinVl,MaxVl)
Looks like the source is "MaskedEditValidator.pre.js"
And BTW the example site masked edit validator for the date (MaskedEditExtender5) is also wrong in that the Mask value is "99/99/99" when it should be "99/99/9999".
If you debug then the value.DateFormat passes "DMY" or the like but the switch statement expects "DayMonthYear". If you use a culture you will use the "short" format. If you specify "DayMonthYear" in the UserDateFormat on the MaskedEditExtender then it works as expected.
The offending function is:
function MaskedEditValidatorPartDate(value,mask,MinVl,MaxVl)
Looks like the source is "MaskedEditValidator.pre.js"
And BTW the example site masked edit validator for the date (MaskedEditExtender5) is also wrong in that the Mask value is "99/99/99" when it should be "99/99/9999".