# 2 Custom intervals

#### Overview

It is possible to create custom rules regarding the times when an item
is checked. The two methods for that are *Flexible intervals*, which
allow to redefine the default update interval, and *Scheduling*, whereby
an item check can be executed at a specific time or sequence of times.

#### Flexible intervals

Flexible intervals allow to redefine the default update interval for
specific time periods. A flexible interval is defined with *Interval*
and *Period* where:

-   *Interval* – the update interval for the specified time period
-   *Period* – the time period when the flexible interval is active (see
    the [time periods](/manual/appendix/time_period) for detailed
    description of the *Period* format)

Up to seven flexible intervals can be defined. If multiple flexible
intervals overlap, the smallest *Interval* value is used for the
overlapping period. Note that if the smallest value of overlapping
flexible intervals is '0', no polling will take place. Outside the
flexible intervals the default update interval is used.

Note that if the flexible interval equals the length of the period, the
item will be checked exactly once. If the flexible interval is greater
than the period, the item might be checked once or it might not be
checked at all (thus such configuration is not advisable). If the
flexible interval is less than the period, the item will be checked at
least once.

If the flexible interval is set to '0', the item is not polled during
the flexible interval period and resumes polling according to the
default *Update interval* once the period is over. Examples:

|Interval|Period|Description|
|--------|------|-----------|
|10|1-5,09:00-18:00|Item will be checked every 10 seconds during working hours.|
|0|1-7,00:00-7:00|Item will not be checked during the night.|
|0|7-7,00:00-24:00|Item will not be checked on Sundays.|
|60|1-7,12:00-12:01|Item will be checked at 12:00 every day. Note that this was used as a workaround for scheduled checks and starting with Zabbix 3.0 it is recommended to use scheduling intervals for such checks.|

#### Scheduling intervals

Scheduling intervals are used to check items at specific times. While
flexible intervals are designed to redefine the default item update
interval, the scheduling intervals are used to specify an independent
checking schedule, which is executed in parallel.

A scheduling interval is defined as:
`md<filter>wd<filter>h<filter>m<filter>s<filter>` where:

-   **md** - month days
-   **wd** - week days
-   **h** - hours
-   **m** - minutes
-   **s** – seconds

`<filter>` is used to specify values for its prefix (days, hours,
minutes, seconds) and is defined as:
`[<from>[-<to>]][/<step>][,<filter>]` where:

-   `<from>` and `<to>` define the range of matching values (included).
    If `<to>` is omitted then the filter matches a `<from> - <from>`
    range. If `<from>` is also omitted then the filter matches all
    possible values.
-   `<step>` defines the skips of the number value through the range. By
    default `<step>` has the value of 1, which means that all values of
    the defined range are matched.

While the filter definitions are optional, at least one filter must be
used. A filter must either have a range or the *<step>* value
defined.

An empty filter matches either '0' if no lower-level filter is defined
or all possible values otherwise. For example, if the hour filter is
omitted then only '0' hour will match, provided minute and seconds
filters are omitted too, otherwise an empty hour filter will match all
hour values.

Valid `<from>` and `<to>` values for their respective filter prefix are:

|Prefix|Description|*<from>*|*<to>*|
|------|-----------|--------------|------------|
|md|Month days|1-31|1-31|
|wd|Week days|1-7|1-7|
|h|Hours|0-23|0-23|
|m|Minutes|0-59|0-59|
|s|Seconds|0-59|0-59|

The `<from>` value must be less or equal to `<to>` value. The `<step>`
value must be greater or equal to 1 and less or equal to `<to>` -
`<from>`.

Single digit month days, hours, minutes and seconds values can be
prefixed with 0. For example `md01-31` and `h/02` are valid intervals,
but `md01-031` and `wd01-07` are not.

In Zabbix frontend, multiple ​scheduling intervals ​are entered in
separate rows. In Zabbix API, they are concatenated into a single string
​with a semicolon `;` ​as a separator.

If a time is matched by several intervals it is executed only once. For
example, `wd1h9;h9` will be executed only once on Monday at 9am.

Examples:

|Interval|Will be executed|
|--------|----------------|
|m0-59|every minute|
|h9-17/2|every 2 hours starting with 9:00 (9:00, 11:00 ...)|
|m0,30 or m/30|hourly at hh:00 and hh:30|
|m0,5,10,15,20,25,30,35,40,45,50,55 or m/5|every five minutes|
|wd1-5h9|every Monday till Friday at 9:00|
|wd1-5h9-18|every Monday till Friday at 9:00,10:00,...,18:00|
|h9,10,11 or h9-11|every day at 9:00, 10:00 and 11:00|
|md1h9m30|every 1st day of each month at 9:30|
|md1wd1h9m30|every 1st day of each month at 9:30 if it is Monday|
|h9m/30|every day at 9:00, 9:30|
|h9m0-59/30|every day at 9:00, 9:30|
|h9,10m/30|every day at 9:00, 9:30, 10:00, 10:30|
|h9-10m30|every day at 9:30, 10:30|
|h9m10-40/30|every day at 9:10, 9:40|
|h9,10m10-40/30|every day at 9:10, 9:40, 10:10, 10:40|
|h9-10m10-40/30|every day at 9:10, 9:40, 10:10, 10:40|
|h9m10-40|every day at 9:10, 9:11, 9:12, ... 9:40|
|h9m10-40/1|every day at 9:10, 9:11, 9:12, ... 9:40|
|h9-12,15|every day at 9:00, 10:00, 11:00, 12:00, 15:00|
|h9-12,15m0|every day at 9:00, 10:00, 11:00, 12:00, 15:00|
|h9-12,15m0s30|every day at 9:00:30, 10:00:30, 11:00:30, 12:00:30, 15:00:30|
|h9-12s30|every day at 9:00:30, 9:01:30, 9:02:30 ... 12:58:30, 12:59:30|
|h9m/30;h10 (*API-specific syntax*)|every day at 9:00, 9:30, 10:00|
|h9m/30<br>h10 (*add this as another row in frontend*)|every day at 9:00, 9:30, 10:00|