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javascriptunix-timestamp

js unix timestamp - set minutes, seconds, milliseconds to zero for resulting timestamp of its hour

Given a unix timestamp such as 1424321864000 (Thu Feb 19 2015 04:57:44 GMT+0000) I would like to convert this to 1424318400000 (Thu Feb 19 2015 04:00:00 GMT+0000).

In other words I want to keep the timestamp exactly as is just remove the minutes, seconds, milliseconds from it. Whatever timestamp is input would return the same timestamp for exactly that day/time 'on its hour'.

Solution

  • There are two ways I can think of doing this. A library such as Luxon can handle this in a fairly straight-forward method:

    const topOfHour = DateTime.fromMillis(initialTimestamp).startOf('hour');

    There's also a matching endOf function if you need that.

    The pure-javascript method works too but is a little messy:

    const initialDate = new Date(initialTimestamp);
const zeroMilliseconds = new Date(initialDate.setMilliseconds(0));
const zeroSeconds = new Date(zeroMilliseconds.setSeconds(0));
const startOfHour = new Date(zeroSeconds.setMinutes(0));

    I want to acknowledge user756659's comment with some slightly more verbose code that I missed when checking documentation.

    const initialDate = new Date(initialTimestamp);
const startOfHour = new Date(initialDate.setMinutes(0, 0, 0))

    It could be pared down to a one-liner, but I'm keeping it verbose here for readability.