//Value parameter - required. All other parameters are optional.
function isDate(value, sepVal, dayIdx, monthIdx, yearIdx) {
    try {
        value = value.replace(/-/g, "/").replace(/\./g, "/");
        var SplitValue = value.split(sepVal || "/");
        if (SplitValue.length != 3) {
            return false;
        }
 
        //Auto  detection of indexes
        if (dayIdx === undefined || monthIdx === undefined || yearIdx === undefined) {
            if (SplitValue[0] > 31) {
                yearIdx = 0;
                monthIdx = 1;
                dayIdx = 2;
            } else {
                yearIdx = 2;
                monthIdx = 1;
                dayIdx = 0;
            }
        }
 
        //Change the below values to determine which format of date you wish to check. It is set to dd/mm/yyyy by default.
        var DayIndex = dayIdx !== undefined ? dayIdx : 0;
        var MonthIndex = monthIdx !== undefined ? monthIdx : 1;
        var YearIndex = yearIdx !== undefined ? yearIdx : 2;
 
        var OK = true;
        if (!(SplitValue[DayIndex].length == 1 || SplitValue[DayIndex].length == 2)) {
            OK = false;
        }
        if (OK && !(SplitValue[MonthIndex].length == 1 || SplitValue[MonthIndex].length == 2)) {
            OK = false;
        }
        if (OK && SplitValue[YearIndex].length != 4) {
            OK = false;
        }
        if (OK) {
            var Day = parseInt(SplitValue[DayIndex], 10);
            var Month = parseInt(SplitValue[MonthIndex], 10);
            var Year = parseInt(SplitValue[YearIndex], 10);
            var MonthDays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
 
            if (OK = (Month <= 12 && Month > 0)) {
 
                var LeapYear = (((Year % 4) == 0) && ((Year % 100) != 0) || ((Year % 400) == 0));
                MonthDays[1] = (LeapYear ? 29 : 28);
 
                OK = Day > 0 && Day <= MonthDays[Month - 1];
            }
        }
        return OK;
    }
    catch (e) {
        return false;
    }
}

http://www.codeproject.com/Tips/144113/JavaScript-Date-Validation

Returns true if the string 'value' is a valid date.

Validate if a string is a Date

javascript, validation

Groovy