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How to manipulate a date that is fetched from an html input with javascript

I am trying to get a date from an html input to javascript, substract 3 years from it and then place the new date back into another html date input field.
I got the substraction to work with the current date but I can not get it to work when I fetch a date from an html input.
Below my code that works:
<input id="InputDate" data-role="datepicker"/>
<input id="OutputDate" data-role="datepicker"/>
<script type="text/javascript">
var dt = new Date(); // this line I want to replace with the next 2 lines!
//var inDate= document.getElementById("InputDate").value;
//var dt = new Date(inDate);
dt.setFullYear(dt.getFullYear() - 3);
var datestring = ("0" + dt.getDate()).slice(-2) + "." + ("0"+(dt.getMonth()+1)).slice(-2) + "." + dt.getFullYear();
document.getElementById("OutputDate").value = datestring;
When I fetch a date from the input field I get 'aN.aN.NaN' back into the output field.
I have tried document.getElementById("InputDate").valueAsDate instead, but this did not work either.
When I place an alert(dt) after the instantiation of dt I get 'Invalid Date'.
Any suggenstions how to get the fetched date in the DateObject correctly?
Regards, Manu

Just need to pass correct format to date() function:
//var dt = new Date(); // this line I want to replace with the next 2 lines!
var inDate= document.getElementById("InputDate").value;
inDate = inDate.split(".");
var dt = new Date(inDate[2],inDate[1],inDate[0]);
//alert(dt);
dt.setFullYear(dt.getFullYear() - 3);
var datestring = ("0" + dt.getDate()).slice(-2) + "." + ("0"+(dt.getMonth()+1)).slice(-2) + "." + dt.getFullYear();
document.getElementById("OutputDate").value = datestring;
<input id="InputDate" data-role="datepicker" value="19.05.2015"/>
<input id="OutputDate" data-role="datepicker"/>

var inputValues = document.getElementById("InputDate").value.split(".");
var dt = new Date(inputValues[2], inputValues[1] - 1, inputValues[0]);
If you get something like 22.12.1985 as InputDate value

first verify your ,document.getElementById("InputDate").value; is
returning correct date
var inDate= document.getElementById("InputDate").value;
var dt = new Date(Date.parse(inDate)); //use parse input to corret date format
dt.setFullYear(dt.getFullYear() - 3);

Use date format
var date = "2017-06-19";//yyyy-mm-dd or mm-dd-yyyy
var dt = new Date(date);
console.log(dt);
//output Mon Jun 19 2017 00:00:00 GMT+0545 (Nepal Standard Time)
// if you want to set the date to new output text box
var newDate = dt.getFullYear() + "-" + (dt.getMonth() + 1) + "-" + dt.getDate();
console.log(newDate);

var d = document;
d.g = d.getElementById;
var inDate = d.g("InputDate");
var outDate = d.g("OutputDate");
var datestring = "";
var mo = "";
var dt = null;
inDate.onchange = function() {
dt = new Date(inDate.value);
dt.setFullYear(dt.getFullYear() - 3);
datestring = ("0" + (dt.getMonth() + 1)).slice(-2) + "." + ("0" + dt.getDate()).slice(-2) + "." + dt.getFullYear();
outDate.value = datestring;
};
<input id="InputDate" data-role="datepicker" value="mm.dd.yyyy"><input id="OutputDate" data-role="datepicker" />
This revision makes use of the onchange event attribute which avoids the "NaN" message displaying in response to the default value of "mm.dd.yyyy" which serves as a prompt for the user. It also uses some short-cuts to reduce the verbosity of the code. Note: while the official example elegantly splits on a "." to get the date values, taking the time to use the Date methods to extract the month, day and year has an advantage despite the extra code. Splitting on a "." works as long as the input data contains a period to demarcate the month, day and year values. But the user could instead use a "/" or a "-" and then that splitting code would not yield the correct result, unless there was code that checked for the period.

How to convert Date format in Javascript

I want to change date format sequence from yy-mm-dd to dd-mm-yy
How can I do it in Javascript ?
I have tried
var now = new Date();
now.format("mm-dd-yy");
But its not working for me

Here is a clear and simple approach
var now = new Date();
var dd = now.getDate(); //returns date
var mm = now.getMonth()+ 1; //returns month and you need to add1 because it is array
var yy = now.getFullYear(); //returns full year
var st = dd + '-' + mm + "-" + yy; //format as string

var dateFormatted = (now.getMonth()+1)+"-"+now.getDate()+"-"+now.getFullYear();

You can use the below mentioned function to format Date
utilities.FormatDate(new Date(),"GMT", "dd/MM/yyyy")

function dateformat(date)
{
var yourdate = new Date(date);
yourdate = yourdate.getDate() + '-' + yourdate.getMonth() +1 + "-" +yourdate.getFullYear();
}
use - or / as you like

Format Date from String in javascript

I have a string that has a date in it and I wan't to be able to convert it.
var startDate = "March-09-2010";
var convertedStartDate = new Date(startDate);
var month = convertedStartDate.getMonth() + 1
var day = convertedStartDate.getDay();
var year = convertedStartDate.getFullYear();
var shortStartDate = month + "-" + day + "-" + year;
alert(shortStartDate);
I want it so it converts March-09-2010 to 09-03-10 (DD-MM-YY)
Anyone know what I am doing wrong?

var startDate = "March-09-2010";
var convertedStartDate = new Date(startDate.replace(/-/g, "/")); // replace hyphen with slash
var month = convertedStartDate.getMonth() + 1
var date = convertedStartDate.getDate();
var year = convertedStartDate.getFullYear();
var shortStartDate = date + "-" + month + "-" + year;
alert(shortStartDate);
demo: http://jsfiddle.net/BjnBW/

Try this:
var dt=Date.parse(Yourstring);
formatDate('DD-MM-YY',dt);
Please check this Date.parse

Check your syntax changed your code a little, modify it according to it then ---
var startDate = "March/09/2010";
var convertedStartDate = new Date(startDate);
var month = convertedStartDate.getMonth() + 1
var day = convertedStartDate.getDate();
var year = convertedStartDate.getFullYear();
var shortStartDate = day+ "-" + month+ "-" + year;
alert(shortStartDate);

your date string is not in the correct format. for correct formats, please see https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date
try this or jsfiddle
var startDate = "March-09-2010";
var tmp = startDate.split('-');
tmp.splice(1, 0, ',');
var convertedStartDate = new Date(tmp.join(' '));
var month = convertedStartDate.getMonth() + 1
var day = convertedStartDate.getDate();
var year = convertedStartDate.getFullYear();
var shortStartDate = ('0' + day).slice(-2) + "-" + ('0' + month).slice(-2) + "-" + year;
alert(shortStartDate);

var shortStartDate =
Globalize.format(Globalize.parseDate(startDate, 'MMMM-dd-yyyy'), 'dd-MM-yy');
Use some library to do the conversion, because the built-in Date.parse() is implementation-dependent. It depends on the system locale what formats it accepts.
The code above uses Globalize.js, which can handle a large number of date formats, including formats with month names in different languages (the default being English).

You'll need to convert 'March' to a number. One way is to use this Array extension to be able to retrieve a month number from a month name:
Array.prototype.enum = function(){
var obj = {};
for (var i=0; i<this.length; (i+=1)) {
obj[this[i]] = i;
}
this.enum = obj;
return this;
};
Now, create an Array with month names
var months = ('January,February,March,April,May,June,July,'+
'August,September,October,November,December').split(',')
.enum();
Now you rewrite your date:
var startDate = "March-09-2010".split(/\-/),
month = months.enum[startDate[0]]+1;
startDate = [startDate[1],
month < 10 ? '0'+month : month,
startDate[2]].join('-');
//=> startDate now is: '09-03-2010'

Use getDateFromFormat() to convert string to date in javascript.
Check this link for more help: http://www.mattkruse.com/javascript/date/

How can I format a json date in dd/mm/yy format in javascript?

I have a json date like \/Date(1334514600000)\/ in my response and when I convert it in javascript then I got this date Tue Apr 17 2012 11:37:10 GMT+0530 (India Standard Time),
but I need the date format like 17/04/2012 and I fail every time. Can anyone tell me how can I resolve it?

I don't think that the other posted answers are quite right, you have already accepted one as working for you so I won't edit it.
Here is an updated version of your accepted answer.
var dateString = "\/Date(1334514600000)\/".substr(6);
var currentTime = new Date(parseInt(dateString ));
var month = currentTime.getMonth() + 1;
var day = currentTime.getDate();
var year = currentTime.getFullYear();
var date = day + "/" + month + "/" + year;
alert(date);
It uses a technique from this answer to extract the epoch from the JSON date.

I found very helpful the row1 answer, however i got stuck on the format for input type="date" as only returns one string for decimals under 10, I was able to modify to work on input type="date", I basically adapted the code from row1 to the code from the link http://venkatbaggu.com/convert-json-date-to-date-format-in-jquery/
I was able through jquery .val add the date to the input
var dateString = "\/Date(1334514600000)\/".substr(6);
var currentTime = new Date(parseInt(dateString));
var month = ("0" + (currentTime.getMonth() + 1)).slice(-2);
var day = ("0" + currentTime.getDate()).slice(-2);
var year = currentTime.getFullYear();
var date = year + '-' + month + '-' + day;
alert(date);

var currentTime = new Date()
var month = currentTime.getMonth() + 1
var day = currentTime.getDate()
var year = currentTime.getFullYear()
var date = day + "/" + month + "/" + year
alert(date);

It's answer to your question...
Build the date object with your timestamp
var currentTime = new Date(1334514600000)
var month = currentTime.getMonth() + 1
var day = currentTime.getDate()
var year = currentTime.getFullYear()
var date = day + "/" + month + "/" + year
alert(date);​
it works
http://jsfiddle.net/ChgUa/

//parse JSON formatted date to javascript date object
var bdate = new Date(parseInt(emp.Birthdate.substr(6)));
//format display date (e.g. 04/10/2012)
var displayDate = $.datepicker.formatDate("mm/dd/yy", bdate);

Easiest way of formatting date is by using pipes if you are using Angular.
Click here
//in .ts file
ngOnInit() {
this.currentDate = new Date()
}
//in html file
<p>Current date is:</p>{{currentDate | date: 'dd/MM/yyyy'}}
//Output: 22/04/2020

Here is an updated version of your accepted answer. DD/MM/YYYY Format Get Try This..
var dateString = "/Date(1623781800000+0530)/"+.substr(6);
var currentTime = new Date(parseInt(dateString));
var month = currentTime.getMonth() + 1;
var day = currentTime.getDate();
var year = currentTime.getFullYear();
if (month.toString().length == 1)
month = "0" + month.toString();
if (day.toString().length == 1){
day = "0" + currentTime.getDate();}
var datenew = day + "/" + month + "/" + year;

var Date = new Date(Tue Jun 15 2021 23:52:47 GMT+0800 (Malaysia Time)).toDateString(); console.log(Date);
Result == Tue Jun 15 2021

How to format dates in javascript

I pick this date from a textbox and i would like to format to this format: yyyy-MM-dd
So from dd/MM/yyyy to yyyy-MM-dd
var startDate = document.getElementById('ctl00_PlaceHolderMain_ctl00_Date').value;
var s = new Date(startDate);
alert(startDate); //which prints out 7/03/2012
//when i use the below to try and format it to : yyyy-MM-dd which is what i want
var scurr_date = s.getDate();
var scurr_month = s.getMonth();
scurr_month++;
var scurr_year = s.getFullYear();
For some reason i get:
var fstartdate = scurr_year + "-" + scurr_month + "-" + scurr_date;
//Output:2012-7-3
instead of : 2012-3-7
also fi i pick a date like 31/12/2011
i get : 2013-7-12
Any ideas what to do.I kind of notice if i use US like 03/07/2012 it kind os works ok.
Thank in advance

You said you want to convert from "dd/MM/yyyy to yyyy-MM-dd". JavaScript's Date constructor will always take the first two digits as a month.
Some regex might help you here:
function fix_date (str) {
var re = /(\d{1,2})\/(\d{1,2})\/(\d{4})/;
str = str.replace(re, function (p1, p2, p3, p4) {
return p4 + '/' + p3 + '/' + p2;
});
return str;
}
var start_date = '7/03/2012';
var new_date = fix_date(start_date);
console.log(new_date); // 2012/03/7​

http://www.webdevelopersnotes.com/tips/html/10_ways_to_format_time_and_date_using_javascript.php3
and this
http://www.elated.com/articles/working-with-dates/
Basically, you have 3 methods and you have to combine the strings for yourself:
getDate(): Returns the date
getMonth(): Returns the month
getFullYear(): Returns the year
<script type="text/javascript">
var d = new Date();
var curr_date = d.getDate();
var curr_month = d.getMonth() + 1; //months are zero based
var curr_year = d.getFullYear();
document.write(curr_date + "-" + curr_month + "-" + curr_year);
</script>
check this answer link