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copy a date object from a user entered date

I am trying to put together a mostly automated form. I have the get current date fine but I am having problems collecting information from a user enter date to place it in another part of the form as well + 1 year. I.E. D.O.B = 08/06/2016 farther down the form expires 08/06/2017. I can make the current date enter automatically but when i try and get the date entered from the user nothing fills the lower date. I tried getting the date using document.getElementById('dob')
function datePone()
{
var date = new Date();
var day = date.getDate(document.getElementById('dob'))
var month = date.getMonth(document.getElementById('dob')) + 1;
var year = date.getFullYear(document.getElementById('dob')) + 1;
if (month < 10) month = "0" + month;
if (day < 10) day = "0" + day;
var oneYear = year + "-" + month + "-" + day;
document.getElementById("dateOneYear").value = oneYear;
}
I've tried using set date or making a new var using document.getElementById('dob') but nothing i have tried has worked so far.

Since "dob" is an input field, to the get the entered data you need to use value property, so try
document.getElementById('dob').value
Also I suggest using momentjs library to manipulate with dates.

Where you have:
var day = date.getDate(document.getElementById('dob'))
the getDate method does not take any arguments, so they are ignored and the above is equivalent to:
var day = date.getDate()
You don't specify what format you're using for the string, "08/06/2016" is ambiguous. Does it represent 8 June or August 6?
You should not use the Date constructor or Date.parse to parse date strings, write your own small function or use a library. Also, adding one year to a date like 29 Feb 2016 will end up on 1 March 2017, so you need to apply a rule to accept that or change it to 28 Feb 2017.
Anyhow, assuming the input is in the format dd/mm/yyyy and you want the output date in the format yyyy-mm-dd, you can use a library or small functions like the following:
// Parse string in d/m/y format
// If invalid, return invalid Date
function parseDMY(s){
var b = s.split(/\D/);
var d = new Date(b[2], --b[1], b[0]);
return d && d.getMonth() == b[1]? d : new Date(NaN);
}
// Return date string in yyyy-mm-dd format
function toISODate(d) {
return d.getFullYear() + '-' +
('0' + (d.getMonth()+1)).slice(-2) + '-' +
('0' + d.getDate()).slice(-2);
}
// Parse string to Date
var d = parseDMY('06/08/2016');
// Add one year
d.setFullYear(d.getFullYear() + 1);
console.log(toISODate(d));
Using a library like fecha.js, you'd parse the string using:
var d = fecha.parse('06/08/2016','DD/MM/YYYY');
and format the output:
fecha.format(d, 'YYYY-MM-DD')

Add a variable number to a date in Java script

I have read a few articles but nothing seems to the point. I have created a form that records a reservation date (when a user wants to reserve a game) and the number of days they hope to borrow it for. I want to add this to the reservation date to get the date the game must be returned by. I have wrapped up my code so far into a function so that I can call it using an onclick method. What should this code look like to work properly? Almost forgot - to make life hard my date is written like this YYYY-MM-DD
function ReturnDate(){
var reservation_begin = document.getElementById('reservation_start').value;
var loan_period = document.getElementById('requested_days').value;
var reservation_end = document.getElementById('return_date');
var dateResult = reservation_begin + loan_period;
return_date.value = dateResult;
}
USING the Suggestions made by Linus
I made the following alterations but had trouble with the formatting of the return date. e.g Setting the reservation date to 2015-01-03 gave me the result of 2015-0-32 for the return date
function ReturnDate(){
var reservation_begin = document.getElementById('reservation_start').value;
var loan_period = document.getElementById('requested_days').value;
var resDate = new Date(reservation_begin);
alert(resDate)
var period = loan_period;
var output = document.getElementById('return_date');
resDate.setDate(resDate.getDate() + period);
alert(period)
//return_date.value = resDate.getFullYear() + "-" + (resDate.getMonth() + 1) + "-" + resDate.getDate();
return_date.value = resDate.getFullYear() + "-" + resDate.getMonth() + "-" + (resDate.getDate() +1);
}

As mentioned dates could be a bit tricky to handle with js.
But to just add days to a date this could be a solution?
JSBIN: http://jsbin.com/lebonababi/1/edit?js,output
JS:
var resDate = new Date('2015-02-01');
var period = 6;
var output = "";
resDate.setDate(resDate.getDate() + period);
output = resDate.getFullYear() + "-" + (resDate.getMonth() + 1) + "-" + resDate.getDate();
alert(output);
EDIT:
Added a new JSBin which is more consistent with the original code.
JSBin: http://jsbin.com/guguzoxuyi/1/edit?js,output
HTML:
<input id="reservationStart" type="text" value="2015-03-01" />
<br />
<input id="requestedDays" type="text" value="14" />
<br />
<a id="calculateDate" href="javascript:;">Calculate Date</a>
<br /><br /><br />
Output:
<input id="calculatedDate" type="text" />
JS:
// Click event
document.getElementById('calculateDate').addEventListener('click', returnDate);
// Click function
function returnDate(){
var reservationStart = document.getElementById('reservationStart').value,
requestedDays = parseInt(document.getElementById('requestedDays').value),
targetDate = new Date(reservationStart),
formattedDate = "";
// Calculate date
targetDate.setDate(targetDate.getDate() + requestedDays);
// Format date
formattedDate = formatDate(targetDate);
// Output date
document.getElementById('calculatedDate').value = formattedDate;
}
// Format date (XXXX-XX-XX)
function formatDate(fullDate) {
var dateYear = fullDate.getFullYear(),
dateMonth = fullDate.getMonth()+1,
dateDays = fullDate.getDate();
// Pad month and days
dateMonth = pad(dateMonth);
dateDays = pad(dateDays);
return dateYear + "-" + dateMonth + "-" + dateDays;
}
// Pad number
function pad(num) {
return (num < 10 ? '0' : '') + num;
}

As per my comment,
Split reservation_begin and use the Date constructor feeding in the
parts to create a Javascript date object. getTime will give you the
milliseconds since the Epoch. There are 86400000 milliseconds in a day, so
multiply this by loan_period. Add the two millisecond result together
and use the Date constructor with your total milliseconds to get
dateResult as a Javascript date object.
using Date.UTC but you don't have to.
function pad(num) {
return num < 10 ? '0' + num : num;
}
var reservation_begin = ('2015-02-01').split('-'),
loan_period = '5',
begin,
end;
reservation_begin[1] -= 1;
begin = new Date(Date.UTC.apply(null, reservation_begin)).getTime();
end = new Date(begin + 86400000 * loan_period);
document.body.textContent = [
end.getUTCFullYear(),
pad(end.getUTCMonth() + 1),
pad(end.getUTCDate())
].join('-');
Why split the date string into parts? This is to avoid cross browser parsing issues.
Why use milliseconds? This is the smallest value represented by Javascript Date, using this will avoid any rollover issues that may be present in browsers.
Why use UTC? You haven't specified the requirements for your script, and this is about as complex as it gets. You don't have to use it, you can just feed the parts into Date and use the non UTC get methods.
What does pad do? It formats the month values to MM and date values to DD.
Note that month is zero referenced in Javascript so months are represent by the numbers 0-11.

A bit confused with the third variable "reservation_end" but according to your question this solution might work.
var dateResult = new Date(reservation_begin);
dateResult.setDate(dateResult.getDate() + parseInt(loan_period));
alert(dateResult);
http://jsfiddle.net/uwfpbzt2/

Example using todays date:
var today = new Date();
today.setDate(today.getDate() + x);
where x is the number of days. Then just use getYear(), getMonth() and getDate() and format it how you like.
EDIT
var myDate = new Date(year, month, day, hours, minutes, seconds, milliseconds);
Assuming your date is entered in dd/mm/yyyy format as inputDate then
dateParts = inputDate.split("/");
var myDate = new Date(dateParts[2], dateParts[1]-1, dateParts[0]);
Depending on the date format your split() delimiter and array positions may be different but this is the general idea.

How to parse date string in jQuery and check if it is in the past

I need to check if the date is in the past. This is what I have so far. JSfiddle here.
var date = "09/12/2013";
var d = new Date();
var month = d.getMonth() + 1;
var day = d.getDate();
var todaysDate = +(('' + day).length < 2 ? '0' : '') + day + '/' + (('' + month).length < 2 ? '0' : '') + month + '/' + d.getFullYear();
if (date < todaysDate) {
alert("in the past");
} else {
alert("in the future");
}
Currently it is saying that the date was in the past, when it should be in the future. I know I need to parse the string as a date, but not sure how.
Help?

With that input format, you can't use a string comparison, because the least significant values are on the left. Note: I'm assuing that date is December 9th, 2013. If you're doing the American thing where it's September 12th, 2013, you'll have to adjust the indexes into parts below.
You could reverse the fields:
var date = "09/12/2013";
var parts = date.split('/');
date = parts[2] + "/" + parts[1] + "/" + parts[0];
...and then do your string comparison (being sure to construct the string for "today" in the same order — year/month/day).
If you're going to do that, you could go ahead and finish the job
var date = "09/12/2013";
var parts = date.split('/');
var date = new Date(parseInt(parts[2], 10), // year
parseInt(parts[1], 10) - 1, // month, starts with 0
parseInt(parts[0], 10)); // day
if (date < new Date()) {
// It's in the past, including one millisecond ago
}
...but of course, if you don't want the expression to be true for one millisecond ago, your string approach is fine.

var date = new Date("09/12/2013");
var d = new Date();
console.log(date>d); // true
var date = new Date("09/12/2011");
console.log(date>d); // false

JavaScript's native Date comparator only works on Date objects, whereas you are comparing Strings. You should parse date into a Date object, and then compare it with d.
//define parse(string) --> Date
if(parse(date) < new Date()) {
alert('past');
} else {
alert('future');
}

Javascript DateDiff

I am having a problem with the DateDiff function. I am trying to figure out the Difference between two dates/times. I have read this posting (What's the best way to calculate date difference in Javascript) and I also looked at this tutorial (http://www.javascriptkit.com/javatutors/datedifference.shtml) but I can't seem to get it.
Here is what I tried to get to work with no success. Could someone please tell me what I am doing and how I can simplify this. Seems a little over coded...?
//Set the two dates
var currentTime = new Date();
var month = currentTime.getMonth() + 1;
var day = currentTime.getDate();
var year = currentTime.getFullYear();
var currDate = month + "/" + day + "/" + year;
var iniremDate = "8/10/2012";
//Show the dates subtracted
document.write('DateDiff is: ' + currDate - iniremDate);
//Try this function...
function DateDiff(date1, date2) {
return date1.getTime() - date2.getTime();
}
//Print the results of DateDiff
document.write (DateDiff(iniremDate, currDate);

Okay for those who would like a working example here is a simple DateDiff ex that tells date diff by day in a negative value (date passed already) or positive (date is coming).
EDIT: I updated this script so it will do the leg work for you and convert the results in to in this case a -10 which means the date has passed. Input your own dates for currDate and iniPastedDate and you should be good to go!!
//Set the two dates
var currentTime = new Date()
var currDate = currentTime.getMonth() + 1 + "/" + currentTime.getDate() + "/" + currentTime.getFullYear() //Todays Date - implement your own date here.
var iniPastedDate = "8/7/2012" //PassedDate - Implement your own date here.
//currDate = 8/17/12 and iniPastedDate = 8/7/12
function DateDiff(date1, date2) {
var datediff = date1.getTime() - date2.getTime(); //store the getTime diff - or +
return (datediff / (24*60*60*1000)); //Convert values to -/+ days and return value
}
//Write out the returning value should be using this example equal -10 which means
//it has passed by ten days. If its positive the date is coming +10.
document.write (DateDiff(new Date(iniPastedDate),new Date(currDate))); //Print the results...

Your first try does addition first and then subtraction. You cannot subtract strings anyway, so that yields NaN.
The second trry has no closing ). Apart from that, you're calling getTime on strings. You'd need to use new Date(...).getTime(). Note that you get the result in milliseconds when subtracting dates. You could format that by taking out full days/hours/etc.

function setDateWeek(setDay){
var d = new Date();
d.setDate(d.getDate() - setDay); // <-- add this
var curr_date = d.getDate();
var curr_month = d.getMonth() + 1;
var curr_year = d.getFullYear();
return curr_date + "-" + curr_month + "-" + curr_year;
}
setDateWeek(1);

No need to include JQuery or any other third party library.
Specify your input date format in title tag.
HTML:
< script type="text/javascript" src="http://services.iperfect.net/js/IP_generalLib.js">
Use javascript function:
IP_dateDiff(strDate1,strDate2,strDateFormat,debug[true/false])
alert(IP_dateDiff('11-12-2014','12-12-2014','DD-MM-YYYY',false));
IP_dateDiff function will return number of days.

Compare day month and year

Good afternoon in my timezone.
I want to compare two dates , one of them is inserted by the user and the other is the present day. Snippet of code :
var dateString = "2012-01-03"
var date = new Date(dateString);
date < new Date() ? true : false;
This returns true, i think under the hood both Date objects are transformed to milliseconds and then compared , and if it is this way the "Today" object is bigger because of the hours and minutes.So what i want to do is compare dates just by the day month and year.What is the best approach ? Create a new Date object and then reset the hours minutes and milliseconds to zero before the comparison? Or extract the day the month and year from both dates object and make the comparison ? Is there any better approach ?
Thanks in advance
With the best regards.
Happy new year

Set the time portion of your created date to zeros.
var d = new Date();
d.setHours(0,0,0,0);

Since it's in yyyy-mm-dd format, you can just build the current yyyy-mm-dd from date object and do a regular string comparison:
var currentDate = new Date();
var year = currentDate.getFullYear();
var month = currentDate.getMonth()+1;
if (month < 10) month = "0" + month;
var day = currentDate.getDate();
if (day < 10) day = "0" + day;
currentDate = year + "-" + month + "-" + day;
var dateString = "2012-01-03"
var compareDates = dateString < currentDate ? true : false;
document.write(compareDates);

A production-ready example based on top of Accepted Answer
Add the following function to your Javascript
Date.prototype.removeTimeFromDate = function () {
var newDate = new Date(this);
newDate.setHours(0, 0, 0, 0);
return newDate;
}
Invoke it whenever you wish to compare
firstDate.removeTimeFromDate() < secondDate.removeTimeFromDate()