if(DateTime.TryParseExact(fieldtext, DATETIMEPATTERN, null, DateTimeStyles.None, out doctime)) {
//DATETIME is a valid DATETIME
}
fieldtext is the string representation of the date eg "23/04/1978", DATETIMEPATTERN is the format "dd/MM/yyyy". doctime will contain a valid DateTime object if the method returns true. For more info, check out the MSDN website. A general hint, work with DateTime objects as much as possible and use the DateTime's ToString method at the very last moment... good luck.
V. No hurries, no worries