How can I run a function at specific time & date?

Question

How can run a function at a given time and date.

Example, I have a function that on the 12th of each month at 10AM, I have a surprise, and I want to tell them this. How can I always have this function running, but only execute at that time?

This page will be running 24/7, as pointed out, apparently this can effect my answer.

Obviously I'd have to compare against the current date, but I'm not sure how to check if the current date and time has been matched.

Shannon

Answer 1

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

Answer 2

maybe use and iframe with meta refresh and workout content server side

<meta http-equiv="refresh" content="{CHANGE_THIS_TO_WHAT_YOU_CALCULATED_AT_SERVER}">

or use javascripts setInterval

var interval = 300000; // run in 5 minutes
window.setInterval("reloadRefresh();", interval);

function reloadRefresh() {
 // do whatever
}

and

Answer 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)
    }
}

Answer 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()

Answer 5

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);
    })();
}