# Time-based schedules for jobs and crawlers
<a name="monitor-data-warehouse-schedule"></a>

You can define a time-based schedule for your crawlers and jobs in Amazon Glue. The definition of these schedules uses the Unix-like [cron](http://en.wikipedia.org/wiki/Cron) syntax. You specify time in [Coordinated Universal Time (UTC)](http://en.wikipedia.org/wiki/Coordinated_Universal_Time), and the minimum precision for a schedule is 5 minutes.

To learn more about configuring jobs and crawlers to run using a schedule, see [Starting jobs and crawlers using triggers](trigger-job.md).

## Cron expressions
<a name="CronExpressions"></a>

Cron expressions have six required fields, which are separated by white space. 

**Syntax**

```
cron({{Minutes}} {{Hours}} {{Day-of-month}} {{Month}} {{Day-of-week}} {{Year}})
```


| **Fields** | **Values** | **Wildcards** | 
| --- | --- | --- | 
| Minutes | 0–59 | , - \* / | 
| Hours | 0–23 | , - \* / | 
| Day-of-month | 1–31 | , - \* ? / L W | 
| Month | 1–12 or JAN-DEC | , - \* / | 
| Day-of-week | 1–7 or SUN-SAT | , - \* ? / L | 
| Year | 1970–2199 | , - \* / | 

**Wildcards**
+ The **,** (comma) wildcard includes additional values. In the `Month` field, `JAN,FEB,MAR` would include January, February, and March.
+ The **-** (dash) wildcard specifies ranges. In the `Day` field, 1–15 would include days 1 through 15 of the specified month.
+ The **\*** (asterisk) wildcard includes all values in the field. In the `Hours` field, **\*** would include every hour.
+ The **/** (forward slash) wildcard specifies increments. In the `Minutes` field, you could enter **1/10** to specify every 10th minute, starting from the first minute of the hour (for example, the 11th, 21st, and 31st minute).
+ The **?** (question mark) wildcard specifies one or another. In the `Day-of-month` field you could enter **7**, and if you didn't care what day of the week the seventh was, you could enter **?** in the Day-of-week field.
+ The **L** wildcard in the `Day-of-month` or `Day-of-week` fields specifies the last day of the month or week.
+ The **W** wildcard in the `Day-of-month` field specifies a weekday. In the `Day-of-month` field, `3W` specifies the day closest to the third weekday of the month.

**Limits**
+ You can't specify the `Day-of-month` and `Day-of-week` fields in the same cron expression. If you specify a value in one of the fields, you must use a **?** (question mark) in the other.
+ Cron expressions that lead to rates faster than 5 minutes are not supported. 

**Examples**  
When creating a schedule, you can use the following sample cron strings.


| Minutes | Hours | Day of month | Month | Day of week | Year | Meaning | 
| --- | --- | --- | --- | --- | --- | --- | 
| 0 | 10 | \* | \* | ? | \* | Run at 10:00 am (UTC) every day | 
| 15 | 12 | \* | \* | ? | \* | Run at 12:15 pm (UTC) every day | 
| 0 | 18 | ? | \* | MON-FRI | \* | Run at 6:00 pm (UTC) every Monday through Friday | 
| 0 | 8 | 1 | \* | ? | \* | Run at 8:00 am (UTC) every first day of the month | 
| 0/15 | \* | \* | \* | ? | \* | Run every 15 minutes | 
| 0/10 | \* | ? | \* | MON-FRI | \* | Run every 10 minutes Monday through Friday | 
| 0/5 | 8–17 | ? | \* | MON-FRI | \* | Run every 5 minutes Monday through Friday between 8:00 am and 5:55 pm (UTC) | 

For example to run on a schedule of every day at 12:15 UTC, specify:

```
cron(15 12 * * ? *)   
```