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

Question

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.

Answer 1

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

Answer 2

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);

Answer 3

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

Answer 4

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, eg 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?