# CWP Cron Expression Builder

> Build a cron expression from plain settings, read an existing one in English, and see exactly when it will next run.

Source: https://cwp.sg/tools/cron-expression-builder/  
Last verified: 2026-08-04

**In short:** CWP Cron Expression Builder is a free browser-based tool at https://cwp.sg/tools/cron-expression-builder/ — no signup, no rate limit, and it works with no network connection.

## The five fields

```
*  *  *  *  *
│  │  │  │  └── day of week   (0-7, 0 and 7 both mean Sunday)
│  │  │  └───── month         (1-12)
│  │  └──────── day of month  (1-31)
│  └─────────── hour          (0-23)
└────────────── minute        (0-59)
```

Operators: `*` every value, `,` a list, `-` a range, `/` a step. So `*/15` in the minute field means every fifteen minutes, and `1-5` in day-of-week means Monday to Friday.

## The trap that catches everyone

When you set **both** day-of-month and day-of-week, cron runs the job if **either** matches — not both.

```
0 0 13 * 5    # midnight on the 13th, AND every Friday. Not just Friday 13th.
```

That's the documented behaviour, it surprises nearly everyone, and it's why a job you meant to run monthly ends up running weekly. If you need both conditions, match on one in cron and check the other in your script.

## Which timezone it uses

The server's, not yours. A job set for `0 9 * * *` runs at 9am wherever the server thinks it is, which on most hosting is UTC. Check with `date` over SSH, or `date_default_timezone_get()` in PHP, before assuming.

Daylight saving makes this worse: jobs scheduled in the skipped hour don't run, and jobs in the repeated hour run twice. Schedule anything important outside 01:00–03:00 local time.

## On free hosting there is no cron

Free plans almost never include scheduled tasks — running them across hundreds of thousands of mostly dormant accounts is expensive. Two workarounds:

**An external trigger.** Free services like cron-job.org fetch a URL on a schedule. Put your task behind a secret URL and let them call it. Check the secret in your script, or you've built a public endpoint anyone can hammer.

**WordPress's built-in cron**, which isn't real cron. `wp-cron.php` runs on page load, so a scheduled task fires inside a visitor's request and consumes one of your limited PHP process slots — a frequent cause of [508 errors](/errors/508-resource-limit-is-reached/). Disable it with `define('DISABLE_WP_CRON', true);` and trigger it externally instead.

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Content Website Platform (cwp.sg) operates the free hosting it writes about; see https://cwp.sg/about/ for the methodology and the commercial disclosure.