Date format validation - dd/mm/yyyy

//Date Validation just copy and paste this code


var dtCh= "/";
var minYear=1900;
var maxYear=2100;

function isInteger(s)
{
var i;
for (i = 0; i < s.length; i++)
{
// Check that current character is number.
var c = s.charAt(i);
if (((c < "0") || (c > "9"))) return false;
}
// All characters are numbers.
return true;
}

function stripCharsInBag(s, bag)
{
var i;
var returnString = "";
// Search through string's characters one by one.
// If character is not in bag, append to returnString.
for (i = 0; i < s.length; i++)
{
var c = s.charAt(i);
if (bag.indexOf(c) == -1) returnString += c;
}
return returnString;
}

function daysInFebruary (year)
{
// February has 29 days in any year evenly divisible by four,
// EXCEPT for centurial years which are not also divisible by 400.
return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
}
function DaysArray(n)
{
for (var i = 1; i <= n; i++)
{
this[i] = 31
if (i==4 || i==6 || i==9 || i==11) {this[i] = 30}
if (i==2) {this[i] = 29}
}
return this
}

function isDate(dtStr)
{
var daysInMonth = DaysArray(12)
var pos1=dtStr.indexOf(dtCh)
var pos2=dtStr.indexOf(dtCh,pos1+1)
var strDay=dtStr.substring(0,pos1)
var strMonth=dtStr.substring(pos1+1,pos2)
var strYear=dtStr.substring(pos2+1)
strYr=strYear
if (strDay.charAt(0)=="0" && strDay.length>1) strDay=strDay.substring(1)
if (strMonth.charAt(0)=="0" && strMonth.length>1) strMonth=strMonth.substring(1)
for (var i = 1; i <= 3; i++) {
if (strYr.charAt(0)=="0" && strYr.length>1) strYr=strYr.substring(1)
}
day=parseInt(strDay)
month=parseInt(strMonth)
year=parseInt(strYr)
if (pos1==-1 || pos2==-1)
{
alert("The date format should be : dd/mm/yyyy")
return false
}
if (strDay.length<1 || day<1 || day>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month])
{
alert("Please enter a valid day")
return false
}
if (strMonth.length<1 || month<1 || month>12)
{
alert("Please enter a valid month")
return false
}
if (strYear.length != 4 || year==0 || yearmaxYear)
{
alert("Please enter a valid 4 digit year between "+minYear+" and "+maxYear)
return false
}
if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false)
{
alert("Please enter a valid date")
return false
}
return true
}