puedes preguntar a doctor google.. pero si prefieres solicitarlo aqui... ten esta es una complicada pero te da una idea
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) && (vDateValue.length >=11)) {
alert("Invalid Date\nPlease Re-Enter");
vDateName.value = "";
vDateName.focus();
vDateName.select();
return false;
}
/*//aditonal code
if(vDateValue.lenth >=11)
alert("Invalid Date");
vDateName.value = "";
vDateName.focus();
vDateName.select();
return false;
}
//additonal code*/
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
