Azure CRON Expression – Cheat Sheet

Overview

If you’re an avid user of the Microsoft Azure cloud, you might have come across CRON expressions for defining schedules.

The CRON expression format originates from Unix-based systems, where it has been used for quite some time. While it is a powerful syntax for expressing schedules, it can sometimes be a bit confusing.

This article will provide you with a quick cheat sheet for using CRON expressions in Azure.

Format

A CRON expression is simply a string consisting of six fields that each define a specific unit of time.

They are written in the following format:

{second} {minute} {hour} {day} {month} {day of the week}

Acceptable Values

The following values are allowed within each date/time unit placeholder.

Field	Allowed Values	Description
{second}	0-59 *	Trigger every {second} second(s)
{minute}	0-59 *	Trigger every {minute} minute(s)
{hour}	0-23 *	Trigger every {hour} hour(s)
{day}	1-31 *	Trigger every {day} day(s) of month
{month}	1-12 *	Trigger every {month} month(s)
{day of week}	0-6 MON-SUN *	Trigger on specific {day of week}

Special Characters

Additionally you can also use the following special characters to build more advanced expressions:

Special Character	Description
*	Trigger on tick of every time unit E.g. ‘*’ in {day} means every day of the month
,	List separator E.g. ‘1,2’ in {month} means every first and second month of the year
–	Specifies a range E.g. ‘5-7’ in {day} means fifth, sixth and seventh of the month
/	Defines an increment E.g. ‘*/10’ in {minute} means every ten minutes.

Examples

Expression	Description
0 * * * * *	Executes every minute
0 0 * * * *	Executes every hour
0 0 0 * * *	Executes every day
0 0 0 0 * *	Executes every month
0 0 0 1 1 *	Executes on first day of Jan each year
30 20 * * SAT	Executes at 08:30pm every Saturday
30 20 * * 6	Executes at 08:30pm every Saturday
0 */5 * * * *	Executes every five minutes
0 0 8-10/1 * * *	Executes every hour between 8am and 10am

Still Stuck?

If you still need a bit more help then why not try this handy CRON to English Translator. It’s great for sanity checking your CRON expressions. Note: I have no affiliation with the developer of this utility so don’t blame me 🙂

https://bradymholt.github.io/cron-expression-descriptor/

Additional Resources

You can find more information about CRON expressions at the below links:

• Microsoft documentation – https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-timer?tabs=csharp
• Wikipedia – https://en.wikipedia.org/wiki/Cron

Final Thoughts

CRON expressions are very powerful however can sometimes be a bit confusing. I hope this article has helped you better understand how to use them.

If you have any thoughts or suggestions, feel free to share them in the comments below.