checkDate()

This function checks if the date is in a valid format (yyyy-mm-dd hh:mm:ss) and if the date actually exists.

function checkDate(date)
{    
    var re = /^\d{4}-\d{2}-\d{2}\s{1}\d{2}:\d{2}:\d{2}$/;            

    var tDate = date.substr(0,10);
    var aDate = tDate.split('-');             
    
    var tTime = date.substr(11,19);
    var aTime = tTime.split(':');                         

    year = aDate[0];
    month = aDate[1] - 1;
    day = aDate[2];             

    hour = aTime[0];
    min = aTime[1];
    sec = aTime[2];             

    // we check here the basic date values
    if ((year < 1980)) {
        return false;
    }

    if (hour > 24) {
        return false;
    }

    if (min > 60) {
        return false;
    }

    if (sec > 60) {
        return false;
    }                      

    sourceDate = new Date(year,month,day);       
    if(year != sourceDate.getFullYear())
    {
        return false;     
    }             

    if(month != sourceDate.getMonth())
    {
        return false;     
    }              

    if(day != sourceDate.getDate())
    {
        return false;     
    }             

    if (!re.test(date)) {
        return false;
    }     
    return true;
}          

getMonthLength()

I use this function everytime i am working with some type of time handling or validation.

function getMonthLength(month,year) {
    var monthlength = new Array(31,28,31,30,31,30,31,31,30,31,30,31);
    if (month==1 && (year/4==Math.floor(year/4) || 
        year/400==Math.floor(year/400)))        
    {
        return 29;
    }
    else return monthlength[month];
}