Develop Reference

Format JSON DateTime

I currently have all my dates being returned with the letter T in my JSON Strings. EX: 2019-02-03T06:48:07. Is there a way to change the JSON String to return as 02-03-2019 06:48:07?
I am also using javascript to load the dates currently into a data table.

You can convert your string into a Date object and then format it like this:
let jsonString = "2019-02-03T06:48:07";
// You should set your own timezone and options.
console.log(new Date(jsonString).toLocaleString('en-US', {hour12: false}))
For more information, visit: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleString

The T is there because this is a standard ISO 8601 format. It makes it very easy to parse on the client side:
var myDate = new Date('2019-02-03T06:48:07')
With myDate you can then do whatever formatting you wish. Assuming you have another function to handle leading zeros, that could be something like:
var myFormattedDate = padLeft(myDate.getMonth() + 1, '0') + '-' +
padLeft(myDate.getDay(), '0') + '-'
myDate.getFullYear() + ' ' +
// etc
Note that your timestamp lacks any timezone information. With this code it will be interpreted on the client side in whatever the local timezone of the user is. If it is UTC time, then you can correct for this by adding either 'Z' or '+00:00' onto the timestamp before parsing in the Date constructor.
If you are able to add a library to assist, this all becomes much easier with moment.js:
myFormattedDate = moment('2019-02-03T06:48:07').format('MM/DD/YYYY HH:mm:ss');

Get "Day" From This Formatted Timestamp In Javascript

I'm working with Javascript within Google Sheets, and I'm having trouble converting or parsing a formatted timestamp, to ultimately extract the day as a numerical value.
My code:
var shopifyTimestamp = "2019-05-18 13:21:17 +0100";
var date = new Date(shopifyTimestamp);
Logger.log(date.getDay());
The output:
[19-06-10 17:40:56:107 BST] NaN
My goal is to extract the day number, for example, "18" from that timestamp.
However, it doesn't seem to convert it. I suspect my timestamp isn't in the correct format for the date() function, so it's about creating a function to parse it.
Hopefully, you can help me with that! :) Thank you so much.

The date object has a method like this for getting the day of the month as a number (1-31).
date.getDate();

18 is date.
var shopifyTimestamp ="2019-05-18 13:21:17 +0100";
var date = new Date(shopifyTimestamp);
console.log(date.getDate());

JavaScript's Date constructor supports ISO 8601 date strings. Without using any libraries, you can do something like this:
var shopifyTimestamp = "2019-05-18 13:21:17 +0100";
// will produce `2019-05-18T13:21:17+0100`
var isoDate = shopifyTimestamp.slice(0, 10)
+ 'T' + shopifyTimestamp.slice(11, 19)
+ shopifyTimestamp.slice(20);
var date = new Date(isoDate);
console.log(date.getDate()); // 18
Also note that you're looking for date.getDate(), rather than date.getDay(). The latter returns the numerical date of the week.

DateTime value passing incorrectly from javascript to C#

I am using the below code to make call to the controller
DateFrom: moment.utc($(".datefrom").val(), "DD/MM/YYYY").toString()
in the ajax call I had a breakpoint and checked what is being passed and the value was
"Wed Jun 20 2018 00:00:00 GMT+0000"
But when I check it in the C#, this is what is getting passed
Other values are getting passed correctly, but this DateFrom has an issue
I checked both the property names and they are exactly the same.
What am I missing?

Always serialize DateTime values using ISO8601 notation. Most libraries, including momentjs, have built in methods for converting a datetime instance to an ISO8601 string and for parsing them from an ISO8601 back to a datetime instance (no additional call needed for momentjs when parsing, the constructor will handle it without additional input).
Keep in mind this is a separate concern from displaying the value on screen. The display and/or edit value should be localized for the user doing the viewing/entry. The serialized value is the value as it is sent between tiers or devices.

This is because javascript use dates as milliseconds since 1970-01-01 and c# 01/01/1900 so in milliseconds there are a big difference.
I suggest you change your string format to dd/MM/yyyy HH:mm:ss.
The best way is converting your date in javascript to a string that c# can recognize.
var date = new Date();
var day = date.getDate(); // yields date
var month = date.getMonth() + 1; // yields month (add one as '.getMonth()' is zero indexed)
var year = date.getFullYear(); // yields year
var hour = date.getHours(); // yields hours
var minute = date.getMinutes(); // yields minutes
var second = date.getSeconds(); // yields seconds
var data= day + "/" + month + "/" + year + " " + hour + ':' + minute + ':' + second;
After that send the "data" to your controller in C#
DateTime date=DateTime.ParseExact(data, "dd/MM/yyyy HH:mm:ss", CultureInfo.InvariantCulture);

Convert Date String(yymmdd) to Date Object in JS

I have a date string in "yymmdd" format i want to convert it into date object in JS
the input string is "161208"
I have tried code below
var mydate = new Date(InputDate);
but it says invalid date.
Here is the fiddle
https://jsfiddle.net/4ry0hL4t/
the basic need is that, I have a date string in "yymmdd" format and i have to convert it to different date formats like ("yyyy/mm/dd, yy-mm-dd","yy/mm").

Check my answer.
Basically you first need to give a proper format to your string. You can either do it manually or use moment.js.
stringFormat = moment(dateObject).format("YYYY-MM-DDTHH:mm:ss");
date = new Date(stringFormat);
This is also really helpful to understand how the different string formats are compatible with different browsers.

I'm not sure if this is what you're after?
var s = '161208';
var dt = new Date('20' + s.substring(0, 2) + '-' + s.substring(2, 4) + '-' + s.substring(4));

Getting next day date for specific string format in Google Apps Script (JavaScript)

Good day everyone!
Working on aprojectmI had to start working with Google Spereadsheet interface and faced a problem I cannot quickly overcome due to not working with JavaScripts ever before.
I have a date in specific format as a string
var date = "2012-08-09";
What I need is to get the next day date as
date = "2012-08-10";
which should include changing not only the day, but month and year too, if necessary.
I've tried using date format
var datum= new Date(date);
datum.setDate(datum.getDate() + 1);
date = datum.toString('yyyy-MM-dd');
but the code appears to fail at writing date to datum variable.
What is the best and quickiest way tosolve this litle problem?
Thanks

The problem when you tag a question 'Javascript' and when you are actually using Google Apps Script is that you get nice answers from people that do not know some special functions available in GAS.
GAS is based on Javascript but Javascript is not GAS... if you see what I mean ;-)
That said, there is actually a "special" function to format date string and I'll show it in the following code.
But there is also another point that could put you into trouble : if you don't mention hours in your date object there is a risk to shift one day if you live in a country that uses daylight savings. This issue has been discussed quite often on this forum and elsewhere so I won't give all the details but it's a good idea to take this into account when you play with date objects. In the code below I extract a tz (time zone) string from the date object we have just created to know if it's in summer or in winter time, then I use this tz string as a parameter in the Utilities.formatDate() method . This guarantees an exact result in every situations.
Here is (finally) the test code :
(use the logger to see results. script editor>view>logs)
function test(){
date = "2012-08-9";
var parts = date.split('-')
var datum = new Date(parts[0],parts[1]-1,parts[2],0,0,0,0);// set hours, min, sec & milliSec to 0
var tz = new Date(datum).toString().substr(25,8);// get the tz string
Logger.log(datum+' in TimeZone '+tz)
datum.setDate(datum.getDate() + 1);// add 1 day
var dateString = Utilities.formatDate(datum,tz,'yyyy-MMM-dd');// show result like you want, see doc for details
Logger.log(dateString);// the day after !
}
Logger results :
Thu Aug 09 2012 00:00:00 GMT+0200 (CEST) in TimeZone GMT+0200
2012-Aug-10

It sounds like a parsing problem you may have better luck, splitting out the date and putting the parameters in individually, any errors you get would be useful:-
var parts = date.split("-");
var datum = new Date(
parseInt(parts[0], 10),
parseInt(parts[1], 10) - 1,
parseInt(parts[2], 10));
There is no built in formatting function for the JavaScript Date object, I'm not sure if the google apps api is any different though. To perform the last line of your code you may either need to write your own functions to extract the data from the JavaScript date object and format it, hint you will also need to write a zerofill function if you want to ensure two digits in your date and month parts of the output.
var formatted = datum.getFullYear() + "-" +
zerofill(datum.getMonth() + 1, 2) + "-" +
zerofill(datum.getDate(), 2);

Passing a format string to toString works in .NET, and it may work in Java, however this doesn't work in Javascript.
Try the following,
var date = "2012-08-09";
var datum = new Date(date);
datum.setDate(datum.getDate() + 1);
date = datum.getFullYear() + "-" + (datum.getMonth() + 1) + "-" + datum.getDate();

Try the following in http://jsfiddle.net/ It works.....
<html>
<head>
<script>
function foo(){
var date = "2012-08-09";
var datum = new Date(date);
datum.setDate(datum.getDate() + 1);
date = datum.getFullYear() + "-" + (datum.getMonth() + 1) + "-" + datum.getDate();
document.getElementById("demo").innerHTML = date;
}
</script>
</head>
<body onload="foo()">
<p id=demo></p>
</body>
</html>​