// Module included in the following assemblies:
//
// assembly-maintenance-time-windows.adoc

[id='con-maintenance-time-window-definition-{context}']
= Maintenance time window definition

You configure maintenance time windows by entering an array of strings in the `Kafka.spec.maintenanceTimeWindows` property.
Each string is a {CronExpression} interpreted as being in UTC (Coordinated Universal Time, which for practical purposes is the same as Greenwich Mean Time).

The following example configures a single maintenance time window that starts at midnight and ends at 01:59am (UTC), on Sundays, Mondays, Tuesdays, Wednesdays, and Thursdays:

[source,yaml,subs="attributes+"]
----
# ...
maintenanceTimeWindows:
  - "* * 0-1 ? * SUN,MON,TUE,WED,THU *"
# ...
----

In practice, maintenance windows should be set in conjunction with the `Kafka.spec.clusterCa.renewalDays` and `Kafka.spec.clientsCa.renewalDays` properties of the `Kafka` resource, to ensure that the necessary CA certificate renewal can be completed in the configured maintenance time windows.

NOTE: {ProductName} does not schedule maintenance operations exactly according to the given windows. Instead, for each reconciliation, it checks whether a maintenance window is currently "open".
This means that the start of maintenance operations within a given time window can be delayed by up to the Cluster Operator reconciliation interval.
Maintenance time windows must therefore be at least this long.

.Additional resources

* For more information about the Cluster Operator configuration, see xref:ref-operators-cluster-operator-configuration-deploying-co[].
