// Check browser version
var isNav4 = false, isNav5 = false, isIE4 = false
var strSeperator = "/";
// If you are using any Java validation on the back side you will want to use the / because 
// Java date validations do not recognize the dash as a valid date separator.
var vDateType = 3; // Global value for type of date format
//                1 = mm/dd/yyyy
//                2 = yyyy/dd/mm  (Unable to do date check at this time)
//                3 = dd/mm/yyyy
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

if(navigator.appName == "Netscape"){
  if (navigator.appVersion < "5"){
    isNav4 = true;
    isNav5 = false;
  }
  else
  if (navigator.appVersion > "4"){
    isNav4 = false;
    isNav5 = true;
  }
} else {
  isIE4 = true;
}

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 = (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("Invalid Date\nPlease Re-Enter");
          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("Invalid Date\nPlease Re-Enter");
            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("Invalid Date\nPlease Re-Enter");
              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("Invalid Date\nPlease Re-Enter");
              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("Invalid Date\nPlease Re-Enter");
          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("Invalid Date\nPlease Re-Enter");
              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("Invalid Date\nPlease Re-Enter");
            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("Invalid Date\nPlease Re-Enter");
          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;
}