How to run a function at specific time & date?

Solution 1:

It's not advised to use setInterval because it has non-deterministic behaviour - events can be missed, or fire all at once. Time will fall out of sync, too.

The code below instead uses setTimeout with a one minute period, where each minute the timer is resynchronised so as to fall as closely to the hh:mm:00.000s point as possible.

function surprise(cb) {
    (function loop() {
        var now = new Date();
        if (now.getDate() === 12 && now.getHours() === 12 && now.getMinutes() === 0) {
            cb();
        }
        now = new Date();                  // allow for time passing
        var delay = 60000 - (now % 60000); // exact ms to next minute interval
        setTimeout(loop, delay);
    })();
}

Solution 2:

On the page where o want to do the check add this

setInterval(function () {
    var date = new Date();
    if (date.getDate() === 12 && date.getHours() === 10 && date.getMinutes === 0) {
        alert("Surprise!!")
    }
}, 1000)

FIDDLE

Update- add date.getSeconds == 0 to limit it to fire only one at 10:00:00. Thanks to comments below

Solution 3:

You can instantiate two Date objects. One for now and one for the next instance of the event. Now is easy: new Date(). For the next instance you can loop through the options till you find one larger than now. Or do some more sophisticated date time wizardry. Compare the getTime() of the both, and then do a setTimeout for the alert.

EDIT: Updated since @Alnitak points out that there's a maximum to the timeout, see setTimeout fires immediately if the delay more than 2147483648 milliseconds.

function scheduleMessage() {
    var today=new Date()

    //compute the date you wish to show the message
    var christmas=new Date(today.getFullYear(), 11, 25)
    if (today.getMonth()==11 && today.getDate()>25)
        christmas.setFullYear(christmas.getFullYear()+1)

    var timeout = christmas.getTime()-today.getTime();
    if( timeout > 2147483647 ){
        window.setTimeout( scheduleMessage(), 2147483647 )
    } else {
        window.setTimeout(function() {alert('Ho Ho Ho!'); scheduleMessage()}, timeout)
    }
}

Solution 4:

You can use something like this

var runned = false;
var d = new Date();
if(d.getDate() == 12 && d.getHours() == 10 && !runned){
    //Do some magic
    runned = true;
}

If you want some with the minute (and not the whole hour you can add d.getMinutes()