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The problem of getting and working with dates in Js [duplicate]

This question already has answers here:
Parsing a string to a date in JavaScript
(35 answers)
Closed 5 months ago.
When working with the task, it became necessary to get dates from html, and to find out the time difference between them:
var now_time_div = document.getElementById("time_now_of");
var start_time_div = document.getElementById("time_when_start_of");
var time_now = now_time_div.textContent || now_time_div.innerHTML;
var time_start = start_time_div.textContent || start_time_div.innerHTML;
After that, without thinking about the format of the data, I wanted to find the time difference in ms:
var worked_time = time_now - time_start
That didn't work, because we are working with a string.
After entering the directory, I found the Date.parse() function, which returns the amount of time that has passed since the given date:
var worked_time = Date.parse(time_start);
but it turned out that it works only with a correctly submitted strig, for example
We need to have:
Date.parse('01 Jan 1970 00:00:00 GMT');
We have:
Date.parse('21.09.2022, 15:34:21')
Maybe someone knows an easy way to implement this without rebuilding the string?

If you don't want to bring in a library like moment.js, you can just massage the date string a bit so it can be parsed correctly
const dateString = '21.09.2022, 15:34:21';
const curDate = dateString.split(',')[0].substring(0, 10).split('.');
const curTime = dateString.split(',')[1];
const parsed = `${curDate[1]}'/'${curDate[0]}'/'${curDate[2]} ${curTime}`;
console.log(new Date(parsed).toString()); // Properly formatted date
You can used this parsed variable to compare to other properly formatted dates

You can use moment.js to parse custom date formats just as in for example Java:
https://momentjs.com/docs/#/parsing/string-format/
After that you can simply convert it to a js date using the toDate function: https://momentjs.com/docs/#/displaying/as-javascript-date/
Edit Example:
var mDate = moment('2022-09-21 10:15:00', 'YYYY-MM-DD HH:mm:ss');
var jsDate = mDate.toDate();

Parsing date YYYYMMDD'T'HHmmss.sss'Z' [duplicate]

This question already has answers here:
Why does Date.parse give incorrect results?
(11 answers)
Closed 3 years ago.
Let's say that I receiving a date from api in format: 20191116T202021.000Z
But unfortunately I'am not able to parse this data in javascript:
var dateToParse = "20191116T202021.000Z"
var dateFormat = "YYYYMMDD'T'HHmmss.sss'Z'"
var test = Date.parse(dateToParse, dateFormat)
console.log(test)
What I want to achieve is to subtract current date with this dateToParse date and see difference in seconds, minutes and days.

There is no second argument support for Date.parse. Instead convert your input string to the ISO format by inserting the missing delimiters:
var dateToParse = "20191116T202021.000Z";
var test = Date.parse(dateToParse.replace(/(....)(..)(..T..)(..)/, "$1-$2-$3:$4:"));
console.log(test); // output as milliseconds
console.log(new Date(test).toJSON()); // output also in JSON format
As noted below, the above regular expression already does the work of parsing the string into its date parts, so you might as well pass those parts to Date.UTC without building another string that needs parsing again. It just needs a little adjustment for the month number:
var dateToParse = "20191116T202021.000Z";
var parts = dateToParse.match(/(....)(..)(..)T(..)(..)(..)\.(...)Z/);
var test = Date.UTC(parts[1], parts[2]-1, parts[3], parts[4], parts[5], parts[6], parts[7]);
console.log(test); // output as milliseconds
console.log(new Date(test).toJSON()); // output also in JSON format
For more efficiency you would just slice the string into its fixed size pieces without the fancy regular expression:
var dateToParse = "20191116T202021.000Z";
var test = Date.UTC(dateToParse.slice(0,4),
dateToParse.slice(4,6)-1,
dateToParse.slice(6,8),
dateToParse.slice(9,11),
dateToParse.slice(11,13),
dateToParse.slice(13,15),
dateToParse.slice(16,19));
console.log(test); // output as milliseconds
console.log(new Date(test).toJSON()); // output also in JSON format

Javascript: How to convert exif date time data to timestamp? [duplicate]

This question already has answers here:
javascript: how to parse a date string
(4 answers)
Closed 5 years ago.
In javascript, while using exif-js to extract metadata of an image file, I am getting date time format as 2017:03:09 14:49:21.
The value in the DateTimeOriginal property is formatted as YYYY:MMY:DD HH:MM:SS. When I use var d = new Date(2017:03:09 14:49:21), it returns NaN. It's the colons in between the YYYY, MM, and DD which causes problem.
How to solve this problem?
Thanks in advance.

Don't use the built-in parser (i.e. Date constructor or Date.parse) for parsing strings as it's largely implementation dependent and unreliable. If you can trust the date to be valid, then the following will do:
/* Parse date string in YYYY-MM-DD hh:mm:ss format
** separator can be any non-digit character
** e.g. 2017:03:09 14:49:21
*/
function parseDate(s) {
var b = s.split(/\D/);
return new Date(b[0],b[1]-1,b[2],b[3],b[4],b[5]);
}
console.log(parseDate('2017:03:09 14:49:21').toString());
It's fairly easy to add validation to the values. Otherwise, use a library and make sure you specify the format to parse.

My recommendation would be to use Moment (http://momentjs.com/docs/), as it provides clean parsing of dates. With Moment, what you want is this:
var tstamp = moment("2017:03:09 14:49:21", "YYYY:MM:DD HH:mm:ss");
var date = tstamp.toDate();

You can do simple string manipulation and create date if the format is always the same, as:
var str = "2017:03:09 14:49:21".split(" ");
//get date part and replace ':' with '-'
var dateStr = str[0].replace(/:/g, "-");
//concat the strings (date and time part)
var properDateStr = dateStr + " " + str[1];
//pass to Date
var date = new Date(properDateStr);
console.log(date);

Date restrictions on user input in JavaScript

I am trying to have a date entry box which has the following restrictions. Date must be today's date or earlier, but not more than 1 year previous. I have the following line:
if (myFDGDT - todayDate > 0 || (myFDGDT - todayDate)/86400000 < -365)
The first portion of that creates the appropriate alert when some enters a date after today's date. Not sure about the best way to cap the entry to a year previous. Attempted a few items, but the above was just an example of my last attempt. This is also written in a dependency and not in the Global JavaScript of our entry client.

Here is a snippet that will generate a Date object that is one year ago. You can compare against it as needed using greater than/less than operators.
var oneyear = new Date('01/01/1971'); // from unix epoch
var now = new Date();
var oneyearago = new Date(now - oneyear);
alert(oneyearago);

If you are manipulating dates a lot in your app you should consider using the momentjs library. For your problem the solution would be something like:
var momentdate = moment(date);
if (momentdate.isAfter(momentdate.add(1, 'year') ||
momentdate.isBefore(momentdate.startOf('day')) {
// Invalid date?
}
Hope this helps.

How to read the correct time/duration values from Google Spreadsheet

I'm trying to get from a time formatted Cell (hh:mm:ss) the hour value, the values can be bigger 24:00:00 for example 20000:00:00 should give 20000:
Table:
if your read the Value of E1:
var total = sheet.getRange("E1").getValue();
Logger.log(total);
The result is:
Sat Apr 12 07:09:21 GMT+00:09 1902
Now I've tried to convert it to a Date object and get the Unix time stamp of it:
var date = new Date(total);
var milsec = date.getTime();
Logger.log(Utilities.formatString("%11.6f",milsec));
var hours = milsec / 1000 / 60 / 60;
Logger.log(hours)
1374127872020.000000
381702.1866722222
The question is how to get the correct value of 20000 ?

Expanding on what Serge did, I wrote some functions that should be a bit easier to read and take into account timezone differences between the spreadsheet and the script.
function getValueAsSeconds(range) {
var value = range.getValue();
// Get the date value in the spreadsheet's timezone.
var spreadsheetTimezone = range.getSheet().getParent().getSpreadsheetTimeZone();
var dateString = Utilities.formatDate(value, spreadsheetTimezone,
'EEE, d MMM yyyy HH:mm:ss');
var date = new Date(dateString);
// Initialize the date of the epoch.
var epoch = new Date('Dec 30, 1899 00:00:00');
// Calculate the number of milliseconds between the epoch and the value.
var diff = date.getTime() - epoch.getTime();
// Convert the milliseconds to seconds and return.
return Math.round(diff / 1000);
}
function getValueAsMinutes(range) {
return getValueAsSeconds(range) / 60;
}
function getValueAsHours(range) {
return getValueAsMinutes(range) / 60;
}
You can use these functions like so:
var range = SpreadsheetApp.getActiveSheet().getRange('A1');
Logger.log(getValueAsHours(range));
Needless to say, this is a lot of work to get the number of hours from a range. Please star Issue 402 which is a feature request to have the ability to get the literal string value from a cell.

There are two new functions getDisplayValue() and getDisplayValues() that returns the datetime or anything exactly the way it looks to you on a Spreadsheet. Check out the documentation here

The value you see (Sat Apr 12 07:09:21 GMT+00:09 1902) is the equivalent date in Javascript standard time that is 20000 hours later than ref date.
you should simply remove the spreadsheet reference value from your result to get what you want.
This code does the trick :
function getHours(){
var sh = SpreadsheetApp.getActiveSpreadsheet();
var cellValue = sh.getRange('E1').getValue();
var eqDate = new Date(cellValue);// this is the date object corresponding to your cell value in JS standard
Logger.log('Cell Date in JS format '+eqDate)
Logger.log('ref date in JS '+new Date(0,0,0,0,0,0));
var testOnZero = eqDate.getTime();Logger.log('Use this with a cell value = 0 to check the value to use in the next line of code '+testOnZero);
var hours = (eqDate.getTime()+ 2.2091616E12 )/3600000 ; // getTime retrieves the value in milliseconds, 2.2091616E12 is the difference between javascript ref and spreadsheet ref.
Logger.log('Value in hours with offset correction : '+hours); // show result in hours (obtained by dividing by 3600000)
}
note : this code gets only hours , if your going to have minutes and/or seconds then it should be developped to handle that too... let us know if you need it.
EDIT : a word of explanation...
Spreadsheets use a reference date of 12/30/1899 while Javascript is using 01/01/1970, that means there is a difference of 25568 days between both references. All this assuming we use the same time zone in both systems. When we convert a date value in a spreadsheet to a javascript date object the GAS engine automatically adds the difference to keep consistency between dates.
In this case we don't want to know the real date of something but rather an absolute hours value, ie a "duration", so we need to remove the 25568 day offset. This is done using the getTime() method that returns milliseconds counted from the JS reference date, the only thing we have to know is the value in milliseconds of the spreadsheet reference date and substract this value from the actual date object. Then a bit of maths to get hours instead of milliseconds and we're done.
I know this seems a bit complicated and I'm not sure my attempt to explain will really clarify the question but it's always worth trying isn't it ?
Anyway the result is what we needed as long as (as stated in the comments) one adjust the offset value according to the time zone settings of the spreadsheet. It would of course be possible to let the script handle that automatically but it would have make the script more complex, not sure it's really necessary.

For simple spreadsheets you may be able to change your spreadsheet timezone to GMT without daylight saving and use this short conversion function:
function durationToSeconds(value) {
var timezoneName = SpreadsheetApp.getActive().getSpreadsheetTimeZone();
if (timezoneName != "Etc/GMT") {
throw new Error("Timezone must be GMT to handle time durations, found " + timezoneName);
}
return (Number(value) + 2209161600000) / 1000;
}
Eric Koleda's answer is in many ways more general. I wrote this while trying to understand how it handles the corner cases with the spreadsheet timezone, browser timezone and the timezone changes in 1900 in Alaska and Stockholm.

Make a cell somewhere with a duration value of "00:00:00". This cell will be used as a reference. Could be a hidden cell, or a cell in a different sheet with config values. E.g. as below:
then write a function with two parameters - 1) value you want to process, and 2) reference value of "00:00:00". E.g.:
function gethours(val, ref) {
let dv = new Date(val)
let dr = new Date(ref)
return (dv.getTime() - dr.getTime())/(1000*60*60)
}
Since whatever Sheets are doing with the Duration type is exactly the same for both, we can now convert them to Dates and subtract, which gives correct value. In the code example above I used .getTime() which gives number of milliseconds since Jan 1, 1970, ... .
If we tried to compute what is exactly happening to the value, and make corrections, code gets too complicated.
One caveat: if the number of hours is very large say 200,000:00:00 there is substantial fractional value showing up since days/years are not exactly 24hrs/365days (? speculating here). Specifically, 200000:00:00 gives 200,000.16 as a result.