var isNav4 = false, isNav5 = false, isIE4 = false
var strSeperator = ".";
var vDateType = 3; // Global value for type of date format
var vYearType = 4; //Set to 2 or 4 for number of digits in the year for Netscape
var vYearLength = 2; // Set to 4 if you want to force the user to enter 4 digits for the year before validating.
var err = 0; // Set the error code to a default of zero

function DateFormat(vDateName, vDateValue, e, dateCheck, dateType) {
   vDateType = dateType;
   // vDateName = object name
   // vDateValue = value in the field being checked
   // e = event
   // dateCheck
   // True  = Verify that the vDateValue is a valid date
   // False = Format values being entered into vDateValue only
   // vDateType
   // 1 = mm/dd/yyyy
   // 2 = yyyy/mm/dd
   // 3 = dd/mm/yyyy
   //Enter a tilde sign for the first number and you can check the variable information.
   if (vDateValue == "~") {
   alert("AppVersion = "+navigator.appVersion+" \nNav. 4 Version = "+isNav4+" \nNav. 5 Version = "+isNav5+" \nIE Version = "+isIE4+" \nYear Type = "+vYearType+" \nDate Type = "+vDateType+" \nSeparator = "+strSeperator);
   vDateName.value = "";
   vDateName.focus();
   return true;
   }
   var whichCode = 0;//(window.Event) ? e.which : e.keyCode;
   // Check to see if a seperator is already present.
   // bypass the date if a seperator is present and the length greater than 8
   if (vDateValue.length > 8 && isNav4) {
   if ((vDateValue.indexOf("-") >= 1) || (vDateValue.indexOf("/") >= 1))
   return true;
   }
   //Eliminate all the ASCII codes that are not valid
   var alphaCheck = " abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ/-";
   if (alphaCheck.indexOf(vDateValue) >= 1) {
   if (isNav4) {
   vDateName.value = "";
   vDateName.focus();
   vDateName.select();
   return false;
   }
   else {
   vDateName.value = vDateName.value.substr(0, (vDateValue.length-1));
   return false;
      }
   }
   if (whichCode == 8) //Ignore the Netscape value for backspace. IE has no value
   return false;
   else {
   //Create numeric string values for 0123456789/
   //The codes provided include both keyboard and keypad values
   var strCheck = '47,48,49,50,51,52,53,54,55,56,57,58,59,95,96,97,98,99,100,101,102,103,104,105';
   if (strCheck.indexOf(whichCode) != -1) {
   if (isNav4) {
   if (((vDateValue.length < 6 && dateCheck) || (vDateValue.length == 7 && dateCheck)) && (vDateValue.length >=1)) {
   alert("Date invalide");
   vDateName.value = "";
   vDateName.focus();
   vDateName.select();
   return false;
   }
   if (vDateValue.length == 6 && dateCheck) {
   var mDay = vDateName.value.substr(2,2);
   var mMonth = vDateName.value.substr(0,2);
   var mYear = vDateName.value.substr(4,4)
   //Turn a two digit year into a 4 digit year
   if (mYear.length == 2 && vYearType == 4) {
   var mToday = new Date();
   //If the year is greater than 30 years from now use 19, otherwise use 20
   var checkYear = mToday.getFullYear() + 30;
   var mCheckYear = '20' + mYear;
   if (mCheckYear >= checkYear)
   mYear = '19' + mYear;
   else
   mYear = '20' + mYear;
   }
   var vDateValueCheck = mMonth+strSeperator+mDay+strSeperator+mYear;
   if (!dateValid(vDateValueCheck)) {
   alert("Date invalide");
   vDateName.value = "";
   vDateName.focus();
   vDateName.select();
   return false;
   }
   return true;
   }
   else {
   // Reformat the date for validation and set date type to a 1
   if (vDateValue.length >= 8  && dateCheck) {
   if (vDateType == 1) // mmddyyyy
   {
   var mDay = vDateName.value.substr(2,2);
   var mMonth = vDateName.value.substr(0,2);
   var mYear = vDateName.value.substr(4,4)
   vDateName.value = mMonth+strSeperator+mDay+strSeperator+mYear;
   }
   if (vDateType == 2) // yyyymmdd
   {
   var mYear = vDateName.value.substr(0,4)
   var mMonth = vDateName.value.substr(4,2);
   var mDay = vDateName.value.substr(6,2);
   vDateName.value = mYear+strSeperator+mMonth+strSeperator+mDay;
   }
   if (vDateType == 3) // ddmmyyyy
   {
   var mMonth = vDateName.value.substr(2,2);
   var mDay = vDateName.value.substr(0,2);
   var mYear = vDateName.value.substr(4,4)
   vDateName.value = mDay+strSeperator+mMonth+strSeperator+mYear;
   }
   //Create a temporary variable for storing the DateType and change
   //the DateType to a 1 for validation.
   var vDateTypeTemp = vDateType;
   vDateType = 1;
   var vDateValueCheck = mMonth+strSeperator+mDay+strSeperator+mYear;
   if (!dateValid(vDateValueCheck)) {
   alert("Date invalide");
   vDateType = vDateTypeTemp;
   vDateName.value = "";
   vDateName.focus();
   vDateName.select();
   return false;
   }
   vDateType = vDateTypeTemp;
   return true;
   }
   else {
   if (((vDateValue.length < 8 && dateCheck) || (vDateValue.length == 9 && dateCheck)) && (vDateValue.length >=1)) {
   alert("Date invalide");
   vDateName.value = "";
   vDateName.focus();
   vDateName.select();
   return false;
          }
        }
      }
   }
   else {
   // Non isNav Check
   if (((vDateValue.length < 8 && dateCheck) || (vDateValue.length == 9 && dateCheck)) && (vDateValue.length >=1)) {
   alert("Date invalide");
   vDateName.value = "";
   vDateName.focus();
   return true;
   }
   // Reformat date to format that can be validated. mm/dd/yyyy
   if (vDateValue.length >= 8 && dateCheck) {
   // Additional date formats can be entered here and parsed out to
   // a valid date format that the validation routine will recognize.
   if (vDateType == 1) // mm/dd/yyyy
   {
   var mMonth = vDateName.value.substr(0,2);
   var mDay = vDateName.value.substr(3,2);
   var mYear = vDateName.value.substr(6,4)
   }
   if (vDateType == 2) // yyyy/mm/dd
   {
   var mYear = vDateName.value.substr(0,4)
   var mMonth = vDateName.value.substr(5,2);
   var mDay = vDateName.value.substr(8,2);
   }
   if (vDateType == 3) // dd/mm/yyyy
   {
   var mDay = vDateName.value.substr(0,2);
   var mMonth = vDateName.value.substr(3,2);
   var mYear = vDateName.value.substr(6,4)
   }
   if (vYearLength == 4) {
   if (mYear.length < 4) {
   alert("Date invalide");
   vDateName.value = "";
   vDateName.focus();
   return true;
      }
   }
   // Create temp. variable for storing the current vDateType
   var vDateTypeTemp = vDateType;
   // Change vDateType to a 1 for standard date format for validation
   // Type will be changed back when validation is completed.
   vDateType = 1;
   // Store reformatted date to new variable for validation.
   var vDateValueCheck = mMonth+strSeperator+mDay+strSeperator+mYear;
   if (mYear.length == 2 && vYearType == 4 && dateCheck) {
   //Turn a two digit year into a 4 digit year
   var mToday = new Date();
   //If the year is greater than 30 years from now use 19, otherwise use 20
   var checkYear = mToday.getFullYear() + 30;
   var mCheckYear = '20' + mYear;
   if (mCheckYear >= checkYear)
   mYear = '19' + mYear;
   else
   mYear = '20' + mYear;
   vDateValueCheck = mMonth+strSeperator+mDay+strSeperator+mYear;
   // Store the new value back to the field.  This function will
   // not work with date type of 2 since the year is entered first.
   if (vDateTypeTemp == 1) // mm/dd/yyyy
   vDateName.value = mMonth+strSeperator+mDay+strSeperator+mYear;
   if (vDateTypeTemp == 3) // dd/mm/yyyy
   vDateName.value = mDay+strSeperator+mMonth+strSeperator+mYear;
   }
   if (!dateValid(vDateValueCheck)) {
   alert("Date invalide");
   vDateType = vDateTypeTemp;
   vDateName.value = "";
   vDateName.focus();
   return true;
   }
   vDateType = vDateTypeTemp;
   return true;
   }
   else {
   if (vDateType == 1) {
   if (vDateValue.length == 2) {
   vDateName.value = vDateValue+strSeperator;
   }
   if (vDateValue.length == 5) {
   vDateName.value = vDateValue+strSeperator;
      }
   }
   if (vDateType == 2) {
   if (vDateValue.length == 4) {
   vDateName.value = vDateValue+strSeperator;
   }
   if (vDateValue.length == 7) {
   vDateName.value = vDateValue+strSeperator;
      }
   }
   if (vDateType == 3) {
   if (vDateValue.length == 2) {
   vDateName.value = vDateValue+strSeperator;
   }
   if (vDateValue.length == 5) {
   vDateName.value = vDateValue+strSeperator;
      }
   }
   return true;
      }
   }
   if (vDateValue.length == 10&& dateCheck) {
   if (!dateValid(vDateName)) {
   // Un-comment the next line of code for debugging the dateValid() function error messages
   //alert(err);
   alert("Date invalide");
   vDateName.focus();
   vDateName.select();
      }
   }
   return false;
   }
   else {
   // If the value is not in the string return the string minus the last
   // key entered.
   if (isNav4) {
   vDateName.value = "";
   vDateName.focus();
   vDateName.select();
   return false;
   }
   else
   {
   vDateName.value = vDateName.value.substr(0, (vDateValue.length-1));
   return false;
       }
     }
   }
}


function dateValid(objName) {
   var strDate;
   var strDateArray;
   var strDay;
   var strMonth;
   var strYear;
   var intday;
   var intMonth;
   var intYear;
   var booFound = false;
   var datefield = objName;
   var strSeparatorArray = new Array("-"," ","/",".");
   var intElementNr;
   // var err = 0;
   var strMonthArray = new Array(12);
   strMonthArray[0] = "Jan";
   strMonthArray[1] = "Feb";
   strMonthArray[2] = "Mar";
   strMonthArray[3] = "Apr";
   strMonthArray[4] = "May";
   strMonthArray[5] = "Jun";
   strMonthArray[6] = "Jul";
   strMonthArray[7] = "Aug";
   strMonthArray[8] = "Sep";
   strMonthArray[9] = "Oct";
   strMonthArray[10] = "Nov";
   strMonthArray[11] = "Dec";
   //strDate = datefield.value;
   strDate = objName;
   if (strDate.length < 1) {
   return true;
   }
   for (intElementNr = 0; intElementNr < strSeparatorArray.length; intElementNr++) {
   if (strDate.indexOf(strSeparatorArray[intElementNr]) != -1) {
   strDateArray = strDate.split(strSeparatorArray[intElementNr]);
   if (strDateArray.length != 3) {
   err = 1;
   return false;
   }
   else {
   strDay = strDateArray[0];
   strMonth = strDateArray[1];
   strYear = strDateArray[2];
   }
   booFound = true;
      }
   }
   if (booFound == false) {
   if (strDate.length>5) {
   strDay = strDate.substr(0, 2);
   strMonth = strDate.substr(2, 2);
   strYear = strDate.substr(4);
      }
   }
   //Adjustment for short years entered
   if (strYear.length == 2) {
   strYear = '20' + strYear;
   }
   strTemp = strDay;
   strDay = strMonth;
   strMonth = strTemp;
   intday = parseInt(strDay, 10);
   if (isNaN(intday)) {
   err = 2;
   return false;
   }
   intMonth = parseInt(strMonth, 10);
   if (isNaN(intMonth)) {
   for (i = 0;i<12;i++) {
   if (strMonth.toUpperCase() == strMonthArray[i].toUpperCase()) {
   intMonth = i+1;
   strMonth = strMonthArray[i];
   i = 12;
      }
   }
   if (isNaN(intMonth)) {
   err = 3;
   return false;
      }
   }
   intYear = parseInt(strYear, 10);
   if (isNaN(intYear)) {
   err = 4;
   return false;
   }
   if (intMonth>12 || intMonth<1) {
   err = 5;
   return false;
   }
   if ((intMonth == 1 || intMonth == 3 || intMonth == 5 || intMonth == 7 || intMonth == 8 || intMonth == 10 || intMonth == 12) && (intday > 31 || intday < 1)) {
   err = 6;
   return false;
   }
   if ((intMonth == 4 || intMonth == 6 || intMonth == 9 || intMonth == 11) && (intday > 30 || intday < 1)) {
   err = 7;
   return false;
   }
   if (intMonth == 2) {
   if (intday < 1) {
   err = 8;
   return false;
   }
   if (LeapYear(intYear) == true) {
   if (intday > 29) {
   err = 9;
   return false;
      }
   }
   else {
   if (intday > 28) {
   err = 10;
   return false;
        }
      }
   }
   return true;
}

function LeapYear(intYear) {
   if (intYear % 100 == 0) {
   if (intYear % 400 == 0) { return true; }
   }
   else {
   if ((intYear % 4) == 0) { return true; }
   }
   return false;
}