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

Question

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.

score 50 · Accepted Answer · answered Aug 25 '11 at 18:45

50

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

answered Aug 25 '11 at 18:45

Tim Down

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Milliseconds will always be `0` this way so `Math.floor` is superfluous I think. – pimvdb Aug 25 '11 at 18:47
Thanks @Tim Down. The other answers seem good also, but as zzzz points out this is shorter and sweeter. – Anthony Jack Aug 25 '11 at 19:06
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Looks like the third line should be: `var timestamp = startOfDay.getTime() / 1000` – Adam C. Jun 08 '17 at 21:37
@AdamC.: That would be fine but there's no need. `startOfDay` is automatically converted via [`valueOf()`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Date/valueOf). See also https://stackoverflow.com/a/9710267/96100. – Tim Down Jun 09 '17 at 15:23
returns undefined. – Venkat Kotra Dec 04 '19 at 17:42
@VenkatKotra: No. `timestamp` contains the timestamp. – Tim Down Dec 05 '19 at 09:41

score 10 · Answer 2 · answered Aug 16 '13 at 16:30

10

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

answered Aug 16 '13 at 16:30

Luis Fontes

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Looks clean, but doesn't work. If you're in GMT+2, the time you will get will be 02:00:00 – AlexG Aug 28 '15 at 12:51

pimvdb · Answer 3 · 2012-02-21T18:22:21.077

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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

edited Feb 21 '12 at 18:22

answered Aug 25 '11 at 18:41

pimvdb

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Is the creation of all those objects really necessary? You can just set hours, minutes and seconds on `now`. – Cristian Vrabie Feb 21 '12 at 17:17
@Cristian Vrabie: Yes, you're correct. Not sure what I was thinking; thanks. – pimvdb Feb 21 '12 at 18:22
shotrer way now.setHours(0,0,0,0); // h , m ,s , ms – yehonatan yehezkel Aug 13 '19 at 15:38

Henry Brewer · Answer 4 · 2014-02-18T12:14:17.963

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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

edited Feb 18 '14 at 12:14

answered Feb 18 '14 at 09:44

Henry Brewer

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score 3 · Answer 5 · answered Sep 16 '15 at 15:45

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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;

answered Sep 16 '15 at 15:45

digitalWestie

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Simple and fast. Love this one – dimcha Aug 04 '21 at 10:33

Alex Turpin · Answer 6 · 2013-07-23T14:43:59.770

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

edited Jul 23 '13 at 14:43

answered Aug 25 '11 at 18:43

Alex Turpin

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If milliseconds is set to `0`, then I don't think `Math.floor` adds much. – pimvdb Aug 25 '11 at 18:44
Indeed. I added it after seeing the other answer, but did not think much about it. – Alex Turpin Aug 25 '11 at 19:44
@Xeon06: Then, why don't you edit your answer and remove it, to not confuse others? :] – trejder Jul 23 '13 at 09:43

score 1 · Answer 7 · answered Aug 25 '11 at 19:05

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());

score 0 · Answer 8 · answered Mar 13 '14 at 04:33

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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);

answered Mar 13 '14 at 04:33

Vu Anh

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score 0 · Answer 9 · answered Jul 16 '17 at 08:15

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();

score 0 · Answer 10 · answered Dec 04 '19 at 17:43

0

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

answered Dec 04 '19 at 17:43

Venkat Kotra

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

10 Answers10