How can I add time to datetime using Javascript?

Question

I have two variables here (datetime and time)

And I want to add the time to the datetime variable.

var datetime = '2020/09/21 09:33:00';
var time = '00:00:23';
var result = datetime + time; // I know this is wrong

How can I add the two variables so that the result will be

2020/09/21 09:33:23

I think you have misread the data. Your datetime should be in the format yyyy/mm/dd hh:mm:ss. So did you actually want ```2020/09.21 9:33:23``` as your output? Or am I misunderstanding something? — The Grand J, Sep 21 '20 at 02:19
that should be actually `var datetime = '2020/09/21 00:09:33';` — Codeblooded Saiyan, Sep 21 '20 at 02:20
You are defining strings, so the `+` will just concatenate. You need the `Date` object. See @Derek.W solution below — GetSet, Sep 21 '20 at 02:22
Does this answer your question? [How to add 30 minutes to a JavaScript Date object?](https://stackoverflow.com/questions/1197928/how-to-add-30-minutes-to-a-javascript-date-object) — The Grand J, Sep 21 '20 at 02:22
sorry I was wrong, that should be `var datetime = '2020/09/21 09:33:00';` — Codeblooded Saiyan, Sep 21 '20 at 02:54

score 3 · Answer 1 · answered Sep 21 '20 at 02:22

3

var date = new Date('2020/09/21 9:33');
var time = 23 * 1000;  // in miliseconds
var result = new Date(date.getTime() + time);

answered Sep 21 '20 at 02:22

Derek Wang

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what if this is the given time? `var time = '00:25:54';` // you mean convert this to milliseconds? – Codeblooded Saiyan Sep 21 '20 at 02:26
Yes. Need to convert to miliseconds like this. `var time = (25 * 60 + 54) * 1000;` – Derek Wang Sep 21 '20 at 02:27
Should be `var time = new Date('1970/01/01 ' + '00:00:23' + ' GMT+0');`, then use `time.getTime()` – Quan To Sep 21 '20 at 02:28

score 0 · Answer 2 · answered Sep 21 '20 at 02:32

So you need to calculate number of seconds and add it to the date

const datetime = '2020/09/21 00:09:33';
const time = '00:00:23';
const parts = time.split(":");
const seconds = +parts[0] * 3600 + +parts[1] * 60 + +parts[2];
const date = new Date(datetime);
date.setSeconds(date.getSeconds() + seconds);

console.log(date.toLocaleString())

How can I add time to datetime using Javascript?

2 Answers2