Filter Hook since 2.1.0

cron_schedules

Registers custom cron interval schedules

Description

cron_schedules is the only way to add a custom recurring interval — WordPress ships with hourly, twicedaily, and daily only.

When it runs

Read whenever wp_get_schedules() is called — typically right before wp_schedule_event() registers a recurring event.

Signature

apply_filters( 'cron_schedules', array $schedules );

Parameters

$schedules array — Existing schedules keyed by interval name, each with 'interval' (seconds) and 'display'.

Examples

Basic

add_filter( 'cron_schedules', function( $schedules ) {
    $schedules['every_fifteen_minutes'] = [
        'interval' => 15 * MINUTE_IN_SECONDS,
        'display'  => 'Every 15 Minutes',
    ];
    return $schedules;
} );

Real case

add_action( 'init', function() {
    if ( ! wp_next_scheduled( 'my_plugin_sync' ) ) {
        wp_schedule_event( time(), 'every_fifteen_minutes', 'my_plugin_sync' );
    }
} );

Schedule an event using the custom interval — this only works once cron_schedules has registered it.

Common Use Cases

Add a custom recurring interval (e.g. every 15 minutes)
Register a weekly or non-standard interval
Match a plugin's own scheduled task frequency
Support finer-grained sync/polling than core's daily/hourly options

Common mistakes

Calling wp_schedule_event() with an interval name that was never registered via cron_schedules — the event is scheduled but silently never runs

Related hooks

Works with init

FAQ

Why does my custom WP-Cron interval never fire?

Usually cron_schedules wasn't hooked before wp_schedule_event() ran, or the interval key name doesn't match exactly — WordPress silently ignores unknown interval names instead of throwing an error.

Source: wp-includes/cron.php

Group wizard

One session: this hook, then each related_hooks entry. Walk it and tell us what to change.

cron_schedules → init

functions.php — cron_schedules

functions.php

<?php
/**
 * Practice: hook into cron_schedules
 */
add_filter( 'cron_schedules', function( $schedules ) {
	// Write your callback here. Always return the value.

	return $schedules;
} );

Group tour

cron_schedules · Hook 1 of 2 · Step 1 of 7

Meet cron_schedules

Registers custom cron interval schedules

cron_schedules is the only way to add a custom recurring interval — WordPress ships with hourly, twicedaily, and daily only.

type filterphase datasince 2.1.0source wp-includes/cron.php

apply_filters( 'cron_schedules', array $schedules );

add_filter( 'cron_schedules', function( $schedules ) {
    $schedules['every_fifteen_minutes'] = [
        'interval' => 15 * MINUTE_IN_SECONDS,
        'display'  => 'Every 15 Minutes',
    ];
    return $schedules;
} );

PHP cron_schedules · Hook 1 of 2 · Step 1 of 7

Practice the cron_schedules WordPress filter hook in our interactive sandbox — a VS Code-style editor with a step-by-step cron_schedules tutorial, add_filter exercises, and instant feedback. No local WordPress install required.