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Calculate time remaining between now and a precise hour of next day

What's the most concise, performant way to get in Javascript the minutes remaining between now, and the upcoming day at 01:00 (am)?
Then, once the current time is after 01:00, I start calculating the difference to the next.

in javascript, a specified date can be provided like this
var date1 = new Date('June 6, 2019 03:24:00');
or it can be specified like this
var date2 = new Date('2019-6-6T03:24:00');
javascript can natively subtract 2 dates
console.log(date1 - date2);
//expected 0;
using this method will output the difference in the dates in milliseconds,
to get minutes you'll want to divide the value by 60000;
so
var futureTime = new Date('2019-06-06T07:24:00');
//there must be a 0 infront of 1 digit numbers or it is an invalid date
var now = new Date();
var difference = (futureTime - now) / 60000;
//get minutes by dividing by 60000
//doing Date() with no arguments returns the current date
read about the javascript Date object here for more information
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date

let now = new Date();
let next1am = new Date();
next1am.setHours(1, 0, 0, 0); // same as now, but at 01:00:00.000
if (next1am < now) next1am.setDate(next1am.getDate() + 1); // bump date if past
let millisecondDiff = next1am - now;
let minuteDiff = Math.floor(millisecondDiff / 1000 / 60);

you can you moment.js here
var current = new Date()
var end = new Date(start.getTime() + 3600*60)// end time to calculate diff
var minDiff = end - start; // in millisec

You can calculate by pure JavaScript:
let today = new Date();
let [y,M,d,h,m,s] = '2019-06-04 05:00:11'.split(/[- :]/);
let yourDate = new Date(y,parseInt(M)-1,d,h,parseInt(m)+30,s);
let diffMs = (yourDate - today);
let diffDays = Math.floor(diffMs / 86400000); // days
let diffHrs = Math.floor((diffMs % 86400000) / 3600000); // hours
let diffMins = (diffDays * 24 * 60)
+ (diffHrs *60)
+ Math.round(((diffMs % 86400000) % 3600000) / 60000); // The overall result
// in minutes
In, addition avoid using the built–in parser for any non–standard format, e.g. in Safari new Date("2019-04-22 05:00:11") returns an invalid date. You really shouldn't even use if for standardized formats as you will still get unexpected results for some formats. Why does Date.parse give incorrect results?

Subtracting a Day from a Full Date

I need to subtract 1 day from a string value of a date I have,
for example when I subtract a day from 2017/01/01 instead of getting 2016/12/31 I end up getting a value of 2017/0/31.
Below is the code I'm working on:
var inputDate = "2017/01/01";
var splitClndr = inputDate.value.split("/");
var clndrDate = new Date(splitClndr[0], splitClndr[1], splitClndr[2]);
clndrDate.setDate(clndrDate.getDate() - 1);
var nd = new Date(clndrDate);
var dd = nd.getDate();
var mm = nd.getMonth();
var y = nd.getFullYear();
var newFormattedDate = y + '/'+ mm + '/'+ dd;
operatorDate.value = newFormattedDate;
The value I get in the variable newFromattedDate is 2017/0/31, how can I make the result of subtracting a day to 2016/12/31 instead?

Months in javascript are zero-based, so 0 is January:
new Date(2017, 1, 1) >> Wed Feb 01 2017
You need to compensate for this, both when creating your clndrDate and when concatenating your string.
new Date(splitClndr[0], splitClndr[1]-1, splitClndr[2])
...
var mm = nd.getMonth()+1;

You can just substract directly from the date:
var d = new Date('2017/01/01');
d.setDate(d.getDate() - 1);
var newDateString = d.toLocaleDateString();
console.log(newDateString);

You can use setDate method to subtract the number of days you want.
var inputDate = "2017/01/01";
var newDate = new Date(inputDate);
newDate.setDate(newDate.getDate() - 1);
console.log(newDate);

Try this,
var inputDate = "2017/01/01";
var splitClndr = inputDate.split("/");
var clndrDate = new Date(splitClndr[0], splitClndr[1] - 1, splitClndr[2]);
var past_time = clndrDate.getTime() - 1000 * 60 * 60 * 24 * 1; // last 1 will be day
clndrDate.setTime(past_time);
console.log(clndrDate);
Working jsfilddle.

Calculate difference between two calendar dates in javascript

I need to calculate difference between two calendar dates. I have gone through various posts but the value returned is not correct.
Heres' my code:-
function getTotalDays()
{
var date11 = document.getElementById("departure_date").value;
var date22 = document.getElementById("arrival_date").value;
var one_day=1000*60*60*24;
var date1 = new Date(date11);
var date2 = new Date(date22);
// Convert both dates to milliseconds
var date1_ms = date1.getTime();
var date2_ms = date2.getTime();
// Calculate the difference in milliseconds
var difference_ms = date2_ms - date1_ms;
// Convert back to days and return
var diffDays = Math.round(difference_ms/one_day);
alert(diffDays);
}
suppse the difference is 2 days its showing as 59.
What's wrong..??

The values you are passing to the date object are likely wrong. Its probably easier for you to do something like this:
var date1 = getDate(date11);
var date2 = getDate(date22);
with getDate being:
function getDate(date) {
//date format dd/mm/yyyy
var dateArr = date.split('/');
var date = new Date(dateArr[2], dateArr[1], dateArr[0]);
return date;
}

how to get difference in year where dates are in yyyy-mm-dd?

i want to get the difference between two dates which are give in yyyy-mm-dd format difference should be in year.
var ds='2002-09-23';
var today_date = new Date();
alert(today_date);
Date.prototype.yyyymmdd = function() {
var mm = (this.getMonth()+1).toString(); // getMonth() is zero-based
var dd = this.getDate().toString();
var dt = yyyy +"-"+(mm[1]?mm:"0"+mm[0]) +"-"+ (dd[1]?dd:"0"+dd[0]);// padding
var num_years = diff_date/31536000000;
alert(num_years);
if (num_years>18){
alert (num_years);
}else{
alert ("i m not 18");
}
please help me out.

This is much shorter:
var yearsApart = new Date(new Date - new Date('2002-09-23')).getFullYear()-1970
… but be careful to take care of non UTC time zones by providing the correct datetime string!

You need no library for this, just pure javascript:
function wholeYearsBetweenTwoDates(dateOneString, dateTwoString) {
// assuming that dateTwo is later in time than dateOne
var dateOne = getDateFromString(dateOneString);
var dateTwo = getDateFromString(dateTwoString);
var result = dateTwo.getFullYear() - dateOne.getFullYear();
dateOne.setFullYear(dateTwo.getFullYear());
if (dateOne > dateTwo) {
// compensate for the case when last year is not full - e.g., when
// provided with '2009-10-10' and '2010-10-09', this will return 0
result -= 1;
}
return result;
}
function getDateFromString(stringDate) {
var dateParts = stringDate.split('-');
var result = new Date(dateParts[0], dateParts[1], dateParts[2]);
return result;
}

Try the following code to get the difference in years...
function getDateDiffInYears(date1, date2) {
var dateParts1 = date1.split('-')
, dateParts2 = date2.split('-')
, d1 = new Date(dateParts1[0], dateParts1[1]-1, dateParts1[2])
, d2 = new Date(dateParts2[0], dateParts2[1]-1, dateParts2[2])
return new Date(d2 - d1).getYear() - new Date(0).getYear() + 1;
}
var diff = getDateDiffInYears('2005-09-23', '2012-07-3');
console.log(diff); // => 7 years
Good luck!

I had been using the formula var yearsApart=milli/milliPerYear but when the day and the month are the same the rounded value is not correct.
Here you have the script I'm using right now ...
function yearDifferenceDates(firstDateDay, firstDateMonth, firstDateYear, secondDateDay, secondDateMonth, secondDateYear) {
var fisrtDate = new Date(firstDateYear, firstDateMonth - 1, firstDateDay);
var secondDate = new Date(secondDateYear, secondDateMonth - 1, secondDateDay);
if(firstDateDay == secondDateDay && (firstDateMonth - 1) == (secondDateMonth - 1)) {
return Math.round((secondDate-fisrtDate)/(1000*60*60*24*365.242199));
}
return Math.floor((secondDate-fisrtDate)/(1000*60*60*24*365.242199));
}

First you have to pick a JavaScript library for parsing dates using a format string (so you can provide date in the format you prefer). Try this great library (at least you do not have to care about implementation details. Date constructor and Date.parse methods must match but it's not mandatory they can parse a simple date in that format).
var date1 = getDateFromFormat("1999-10-10", "YYYY-MM-DD");
var date2 = getDateFromFormat("2012-10-10", "YYYY-MM-DD");
Then, when you have to calculate the difference:
var millisecondsPerSecond = 1000;
var millisecondsPerMinute = millisecondsPerSecond * 60;
var millisecondsPerHour = millisecondsPerMinute * 60;
var millisecondsPerDay = millisecondsPerHour * 24;
var millisecondsPerYear = millisecondsPerDay * 365.26;
var years = Math.round((date2 - date1) / millisecondsPerYear);
If you need a raw calculation you can use getFullYear() directly.

You can compare dates more easily if you convert them to their millisecond values.
var birthday = new Date('2002-09-23');
var now = new Date();
var age = now.getTime() - birthday.getTime();
if (age < (1000 * 60 * 60 * 24 * 365 * 18)) { // number of milliseconds in 18 years
document.write('not over 18');
} else {
document.write('over 18');
}

Above has a little bug but this work :)
NOT WORKING: var millisecondsPerHour = millisecondsPerMinute = 60;
WORKING FINE: var millisecondsPerHour = millisecondsPerMinute * 60;
But thx Adriano Repetti
Here the complete code (with dot Format)
var date1 = "01.01.2014";
var date2 = "31.12.2016";
var date1 = date1.split(".");
var date2 = date2.split(".");
date1 = String(date1[2] +"-"+ date1[1] +"-"+ date1[0]);
date2 = String(date2[2] +"-"+ date2[1] +"-"+ date2[0]);
var date1 = Date.parse(date1);
var date2 = Date.parse(date2);
//(Not for Europa :) )
//var date1 = Date.parse("2014-01-01");
//var date2 = Date.parse("2016-12-31");
var millisecondsPerSecond = 1000;
var millisecondsPerMinute = millisecondsPerSecond * 60;
var millisecondsPerHour = millisecondsPerMinute * 60;
var millisecondsPerDay = millisecondsPerHour * 24;
var millisecondsPerYear = millisecondsPerDay * 365.26;
// IN YEARS
var years = (date2 - date1) / millisecondsPerYear;
// IN MONTHS
var month = years * 12 // Very tricky, I know ;)

var d1=new Date(2002, 9, 23);
var d2=new Date();
var milli=d2-d1;
var milliPerYear=1000*60*60*24*365.26;
var yearsApart=milli/milliPerYear;
console.log(yearsApart)

How do you get the unix timestamp for the start of today in javascript?

I realize that the current timestamp can be generated with the following...
var timestamp = Math.round((new Date()).getTime() / 1000);
What I'd like is the timestamp at the beginning of the current day. For example the current timestamp is roughly 1314297250, what I'd like to be able to generate is 1314230400 which is the beginning of today August 25th 2011.
Thanks for your help.

var now = new Date();
var startOfDay = new Date(now.getFullYear(), now.getMonth(), now.getDate());
var timestamp = startOfDay / 1000;

Well, the cleanest and fastest way to do this is with:
long timestamp = 1314297250;
long beginOfDay = timestamp - (timestamp % 86400);
where 86400 is the number of seconds in one day

var now = new Date; // now
now.setHours(0); // set hours to 0
now.setMinutes(0); // set minutes to 0
now.setSeconds(0); // set seconds to 0
var startOfDay = Math.floor(now / 1000); // divide by 1000, truncate milliseconds

var d = new Date();
d.setHours(0);
d.setMinutes(0);
d.setSeconds(0);
d.setMilliseconds(0);
var t = d / 1000;

Alternatively you could subtract the modulo of a days length in miliseconds e.g.
var day = 24*60*60*1000;
var start_of_today = Date.now() - Date.now() % day;

Luis Fontes' solution returns UTC time so it can be 1 hour (daylight saving time) different from setHours solution.
var d = new Date();
var t = d - (d % 86400000);
Simplified version of examples above (local time).
var d = new Date();
d.setHours(0,0,0,0);
var t = d / 1000;
Here you can find some performance tests: http://jsperf.com/calc-start-of-day

Another alternative for getting the beginning of the day is the following:
var now = new Date();
var beginningOfDay = new Date(now.getTime() -
now.getHours() * 60 * 60 * 1000 -
now.getMinutes() * 60 * 1000 -
now.getSeconds() * 1000 -
now.getMilliseconds());

var yoursystemday = new Date(new Date().getTime()-(120000*60+new Date().getTimezoneOffset()*60000));
yoursystemday = new Date();
var current_time_stamp = Math.round(yoursystemday.getTime()/1000);

For any date it's easy to get Timestamps of start/end of the date using ISO String of the date ('yyyy-mm-dd'):
var dateString = '2017-07-13';
var startDateTS = new Date(`${dateString}T00:00:00.000Z`).valueOf();
var endDateTS = new Date(`${dateString}T23:59:59.999Z`).valueOf();
To get ISO String of today you would use (new Date()).toISOString().substring(0, 10)
So to get TS for today:
var dateString = (new Date()).toISOString().substring(0, 10);
var startDateTS = new Date(`${dateString}T00:00:00.000Z`).valueOf();
var endDateTS = new Date(`${dateString}T23:59:59.999Z`).valueOf();

var now = new Date();
var startOfDay = new Date(now.getFullYear(), now.getMonth(), now.getDate());
var timestamp = startOfDay.getTime() / 1000;