Set intervals with greater precision

Usage no npm install needed!

<script type="module">
  import setSaferInterval from '';



This project is an attempt to allow interval setting which can be updated closer to the arriving time to occur at a greater frequency.


npm i set-safer-interval


Here we set a timer to run every 50 minutes, but when reaching the desired hour, we check whether we are under 15 minutes past the hour, and if so, we increment the next interval step to run in 40 minutes (as we know that should be safe not to overpass the hour). If we were to run it at that time, we would risk running it twice (50 minutes later could still be within the hour). Finally, if it is equal to or over 15 minutes, we run the desired function and return to incrementing on intervals of 50 minutes (until the same hour on the next day).

We could perform a more complex check to increment at a more fine-tuned range, so that we narrowed things down running at minute and/or second intervals, for example.

import setSaferInterval from 'set-safer-interval';

const fortyMinutesInMilliseconds = 40 * 60 * 1000;
const fiftyMinutesInMilliseconds = 50 * 60 * 1000;

// The `interval` is just passsed in for a convenience. It equals
//  `fiftyMinutesInMilliseconds`
const clear = setSaferInterval((interval) => {
  const date = new Date();
  // 12pm UTC == 8am EST (8:00am-8:59am)
  if (date.getUTCHours() === 12) { // 0-23 UTC
    // To avoid running twice in the hour, bump forty minutes before
    //   next check
    if (date.getUTCMinutes() < 15) {
      // We landed under 15 minutes, so jumping 40
      return fortyMinutesInMilliseconds - interval;

    // 8:15am-8:59am EST (so safe to increment 50 minutes without
    //   recurring within the 8am EST (12pm UTC) window)

  // Keep normal supplied interval (`fiftyMinutesInMilliseconds`); we could
  //   also just return `undefined`
  return 0;
}, fiftyMinutesInMilliseconds);

// You can optionally clear the "interval" later (behind the scenes, it
//   actually  calls `clearTimeout` against the last `setTimeout` call)
// clear();


The changelog can be found on

Authors and license

Brett Zamir and contributors.

MIT License, see the included LICENSE-MIT.tx file.


  1. See about using mockdate for tests: and uncomment above reference in README if available