Develop Reference

Javascript function to calculate the hours remaining to specific date or time

I need to count the remaining time in hours between today or actual date/time and a specific end date at 00:00 hrs.
I tried in this fiddle, but I get the counting of one month more than it should be.
https://jsfiddle.net/alonsoct/52ts89mz/
var endTime = new Date(2019,10,18,0,0,0) / 1000;
function setClock() {
var elapsed = new Date() / 1000;
var totalTime = endTime - elapsed;
var hr = parseInt(totalTime / 3600)
var min = parseInt(totalTime / 60) % 60;
var sec = parseInt(totalTime % 60, 10);
var result = hr + " hours, " + min + " minutes " + sec + " seconds";
document.getElementById('timeRemaining').innerHTML = result;
setTimeout(setClock, 1000);
}
setClock();
If I enter one month less in the "endTime" variable I get the correct result in hours count, but this is not fine I need to enter the real end date without the need to subtract one month.
Thanks

The code below is mostly your code with one change. I changed the input for endTime to an ISO format and omitted the time Zone. This, in theory, will default to your browser's timezone. I tested on your linked and it worked. Here is some additional information https://www.w3schools.com/js/js_date_formats.asp
var endTime = new Date("2019-10-18T00:00:00") / 1000;
function setClock() {
var elapsed = new Date() / 1000;
var totalSec = endTime - elapsed;
var h = parseInt( totalSec / 3600 )
var m = parseInt( totalSec / 60 ) % 60;
var s = parseInt(totalSec % 60, 10);
var result = h + " hours, " + m + " minutes " + s + " seconds";
document.getElementById('timeRemaining').innerHTML = result;
setTimeout(setClock, 1000);
}
setClock();

Here is a working solution with Vanilla JS:
var calcTime = setInterval(function(){
date_future = new Date(2019,10,18,0,0,0)
date_now = new Date();
seconds = Math.floor((date_future - (date_now))/1000);
minutes = Math.floor(seconds/60);
hours = Math.floor(minutes/60);
days = Math.floor(hours/24);
hours = hours-(days*24);
minutes = minutes-(days*24*60)-(hours*60);
seconds = seconds-(days*24*60*60)-(hours*60*60)-(minutes*60);
It's pretty easier with JQuery → http://hilios.github.io/jQuery.countdown/examples/show-total-hours.html

JavaScript counts months from 0 to 11.
January is 0. December is 11.
I think you were thinking that endTime will be October 18th, 2019 but actually it's November 18th, 2019.
You can see more relevant information here.
https://www.w3schools.com/js/js_dates.asp
Thanks.

If between the start-datetime and end-datetime a change takes place in winter / summertime remember to make summertime/wintertime adjustments
(if you get these values from e.g. an api:) if the startdate is specified by a client in location x and enddate is specified in location y, you have take into account that the startdate could potentially be in 00:00:00+14:00 timezone and end the endate in max -14 timezone.
if you only present 2 timeboxes: time 1 and time 2, you can map these anywhere on a 52 hours time-scale: -14 , +14 and the 24 hours gmt timescale where you then would normalize to. ( 0:00 could mean i am in Samoa +14, 14 hours ahead of the end of GMT 23:59:59 (14 further) or ahead of GMT 0:00 (14+24 further). Then there are countries which make local time decisions e.g. in India with +5.5 UTC or Burma +6.5 or newfoundland -3.5.
Since this is stackexchange and people will copy and paste these examples in their applications even if these applications are "on the internet" and so DO have users from every location in the world.
Therefore ... use a library: https://momentjs.com/ ; Get hours difference between two dates in Moment Js they have a helper https://momentjs.com/docs/#/displaying/to/ and see also: Moment.js - How To Detect Daylight Savings Time And Add One Day
You can see the same bug on https://www.timeanddate.com/countdown but they added in words : https://www.timeanddate.com/countdown/one-hour-offwintertijd (and they assume the end datetime is in the same location as the countdown datetime)

How to get current day count of the quarter [duplicate]

I have two input dates taking from Date Picker control. I have selected start date 2/2/2012 and end date 2/7/2012. I have written following code for that.
I should get result as 6 but I am getting 5.
function SetDays(invoker) {
var start = $find('<%=StartWebDatePicker.ClientID%>').get_value();
var end = $find('<%=EndWebDatePicker.ClientID%>').get_value();
var oneDay=1000 * 60 * 60 * 24;
var difference_ms = Math.abs(end.getTime() - start.getTime())
var diffValue = Math.round(difference_ms / oneDay);
}
Can anyone tell me how I can get exact difference?

http://momentjs.com/ or https://date-fns.org/
From Moment docs:
var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 28]);
a.diff(b, 'days') // =1
or to include the start:
a.diff(b, 'days')+1 // =2
Beats messing with timestamps and time zones manually.
Depending on your specific use case, you can either
Use a/b.startOf('day') and/or a/b.endOf('day') to force the diff to be inclusive or exclusive at the "ends" (as suggested by #kotpal in the comments).
Set third argument true to get a floating point diff which you can then Math.floor, Math.ceil or Math.round as needed.
Option 2 can also be accomplished by getting 'seconds' instead of 'days' and then dividing by 24*60*60.

If you are using moment.js you can do it easily.
var start = moment("2018-03-10", "YYYY-MM-DD");
var end = moment("2018-03-15", "YYYY-MM-DD");
//Difference in number of days
moment.duration(start.diff(end)).asDays();
//Difference in number of weeks
moment.duration(start.diff(end)).asWeeks();
If you want to find difference between a given date and current date in number of days (ignoring time), make sure to remove time from moment object of current date as below
moment().startOf('day')
To find difference between a given date and current date in number of days
var given = moment("2018-03-10", "YYYY-MM-DD");
var current = moment().startOf('day');
//Difference in number of days
moment.duration(given.diff(current)).asDays();

Try this Using moment.js (Its quite easy to compute date operations in javascript)
firstDate.diff(secondDate, 'days', false);// true|false for fraction value
Result will give you number of days in integer.

Try:
//Difference in days
var diff = Math.floor(( start - end ) / 86400000);
alert(diff);

This works for me:
const from = '2019-01-01';
const to = '2019-01-08';
Math.abs(
moment(from, 'YYYY-MM-DD')
.startOf('day')
.diff(moment(to, 'YYYY-MM-DD').startOf('day'), 'days')
) + 1
);

I made a quick re-usable function in ES6 using Moment.js.
const getDaysDiff = (start_date, end_date, date_format = 'YYYY-MM-DD') => {
const getDateAsArray = (date) => {
return moment(date.split(/\D+/), date_format);
}
return getDateAsArray(end_date).diff(getDateAsArray(start_date), 'days') + 1;
}
console.log(getDaysDiff('2019-10-01', '2019-10-30'));
console.log(getDaysDiff('2019/10/01', '2019/10/30'));
console.log(getDaysDiff('2019.10-01', '2019.10 30'));
console.log(getDaysDiff('2019 10 01', '2019 10 30'));
console.log(getDaysDiff('+++++2019!!/###10/$$01', '2019-10-30'));
console.log(getDaysDiff('2019-10-01-2019', '2019-10-30'));
console.log(getDaysDiff('10-01-2019', '10-30-2019', 'MM-DD-YYYY'));
console.log(getDaysDiff('10-01-2019', '10-30-2019'));
console.log(getDaysDiff('10-01-2019', '2019-10-30', 'MM-DD-YYYY'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.js"></script>

Also you can use this code: moment("yourDateHere", "YYYY-MM-DD").fromNow(). This will calculate the difference between today and your provided date.

// today
const date = new Date();
// tomorrow
const nextDay = new Date(new Date().getTime() + 24 * 60 * 60 * 1000);
// Difference in time
const Difference_In_Time = nextDay.getTime() - date.getTime();
// Difference in Days
const Difference_In_Days = Difference_In_Time / (1000 * 3600 * 24);

Show JavaScript date - datetimeoffset(7) in database

The date is stored in the database as datetimeoffset(7).
The MVC controller gets the date from the database in the format "10/8/2015 6:05:12 PM -07:00" and passes it to the view as it is. I am trying to convert it to the correct date to show that in the view as mm/dd/yyy by doing the following:
var myDate = "10/8/2015 6:05:12 PM -07:00";
var newDate = New Date(myDate);
Then I'm formatting it to mm/dd/yyyy format after extracting the day, month and year.
IE11 and Safari do not like this and show error "Invalid date" in the console at the line
var newDate = New Date(myDate)
Chrome or Firefox doesn't show any problems.
Now I know that "10/8/2015 6:05:12 PM -07:00" is not a valid datestring. So my question is, how to handle this situation so all major browsers will show the correct date?

This function should work, I'm aware it needs some refactoring but it may be a good starting point.
function readDate(inputDate) {
// extract the date that can be parsed by IE ("10/8/2015 6:05:12 PM")
// and the timezone offset "-07:00"
var parsedDate = /([\s\S]*?)\s*([+-][0-9\:]+)$/.exec(inputDate);
//create new date with "datetimeoffset" string
var dt = new Date(parsedDate[1]);
// get millisecs
var localTime = dt.getTime();
// get the offset in millisecs
// notice the conversion to milliseconds
// the variable "localTzOffset" can be negative
// because the standar (http://www.w3.org/TR/NOTE-datetime)
var localTzOffset = dt.getTimezoneOffset() * 60 * 1000;
// to get UTC time
var utcTime = localTime + localTzOffset;
// extract hours and minutes difference
// for given timezone
var parsed = /([+-][0-9]+)\:([0-9]+)/.exec(parsedDate[2]);
var hours = parseInt(parsed[1]);
var minutes = parseInt(parsed[2]);
// convert extracted difference to milliseconds
var tzOffset = Math.abs(hours * 60 * 60 * 1000) + (minutes * 60 * 1000);
// taking into accout if negative
tzOffset = hours > 1 ? tzOffset : tzOffset * -1;
// construct the result Date
return new Date(utcTime + tzOffset);
}
Usage:
var date = readDate("10/8/2015 6:05:12 PM -07:00");

Javascript and mySQL dateTime stamp difference

I have a mySQL database in which I store the time in this format automatically:
2015-08-17 21:31:06
I am able to retrieve this time stamp from my database and bring it into javascript. I want to then get the current date time in javascript and determine how many days are between the current date time and the date time I pulled from the database.
I found this function when researching how to get the current date time in javascript:
Date();
But it seems to return the date in this format:
Tue Aug 18 2015 10:49:06 GMT-0700 (Pacific Daylight Time)
There has to be an easier way of doing this other than going character by character and picking it out from both?

You can build a new date in javascript by passing the data you receive from your backend as the first argument.
You have to make sure that the format is an accepted one. In your case we need to replace the space with a T. You may also be able to change the format from the back end.
Some good examples are available in the MDN docs.
var d = new Date("2015-08-17T21:31:06");
console.log(d.getMonth());
To calculate the difference in days you could do something like this:
var now = new Date();
var then = new Date("2015-08-15T21:31:06");
console.log((now - then)/1000/60/60/24);

You can select the difference directly in your query:
SELECT DATEDIFF(now(), myDateCol) FROM myTable;

the Date object has a function called getTime(), which will give you the current timestamp in milliseconds. You can then get the diff and convert to days by dividing by (1000 * 3600 * 24)
e.g.
var date1 = new Date()
var date2 = new Date()
var diffInMs = date2.getTime() - date1.getTime()
var diffInDays = diffInMs/(1000*3600*24)

Since none of the other answer got it quite right:
var pieces = "2015-08-17 21:31:06".split(' ');
var date = pieces[0].split('-');
var time = pieces[1].split(':');
var yr = date[0], mon = date[1], day = date[2];
var hour = time[0], min = time[1], sec = time[2];
var dateObj = new Date(yr, mon, day, hr, min, sec);
//if you want the fractional part, omit the call to Math.floor()
var diff = Math.floor((Date.now() - dateObj.getTime()) / (1000 * 60 * 60 * 24));
Note that none of this deals with the timezone difference between the browser and whatever you have stored in the DB. Here's an offset example:
var tzOff = new Date().getTimezoneOffset() * 60 * 1000; //in ms

Get date time for a specific time zone using JavaScript

It seems that JavaScript's Date() function can only return local date and time. Is there anyway to get time for a specific time zone, e.g., GMT-9?
Combining #​Esailija and #D3mon-1stVFW, I figured it out: you need to have two time zone offset, one for local time and one for destination time, here is the working code:
var today = new Date();
var localoffset = -(today.getTimezoneOffset()/60);
var destoffset = -4;
var offset = destoffset-localoffset;
var d = new Date( new Date().getTime() + offset * 3600 * 1000)
An example is here: http://jsfiddle.net/BBzyN/3/

var offset = -8;
new Date( new Date().getTime() + offset * 3600 * 1000).toUTCString().replace( / GMT$/, "" )
"Wed, 20 Jun 2012 08:55:20"
<script>
var offset = -8;
document.write(
new Date(
new Date().getTime() + offset * 3600 * 1000
).toUTCString().replace( / GMT$/, "" )
);
</script>

You can do this in one line:
let d = new Date(new Date().toLocaleString("en-US", {timeZone: "timezone id"})); // timezone ex: Asia/Jerusalem

var today = new Date();
var offset = -(today.getTimezoneOffset()/60);

You can always get GMT time (so long as the client's clock is correct).
To display a date in an arbitrary time-zone, construct a string from the UTC hours, minutes, and seconds after adding the offset.

There is simple library for working on timezones easily called TimezoneJS can be found at https://github.com/mde/timezone-js.