The disadvantage is that client-side scripting is optional on browsers and sometimes poorly supported.
Causes any date entered in the specified field to be validated as a valid date (date, time and date/time are supported).
Use of the date rule requires that a valid format attribute also be included for the field.
The format is used to both validate and format the input. The pattern can be given as a named pattern or as a Perl compatible regular expression.
Rather, it must be validated by what it looks like: its pattern.
By utilizing PHP's Perl compatible regular expresssion syntax, we are able to easily implement a pattern matching validation rule.
All elements on the current form are processed for errors at the same time.