Monthly maintenance has two modes:

• By day of month
• By day of week

For both of these, we have to specify the start time and the length of the maintenance period, the same as in daily and weekly maintenance modes. Additionally, we have to choose which months the maintenance will happen in—we may choose one month or more. In Day of month mode (option Date set to Day of month), we have to enter a day in the Day of month field. Maintenance will happen on that day only in each of the months we select.

In Day of week mode (option Date set to Day of week), we have to choose which days of the week the maintenance will take place on—we may choose one or more:

As this has to happen monthly, not weekly, we also have to choose whether this will happen on the first, second, third, fourth, or last weekday in any of the selected months:

In addition to this, we may also ask Zabbix to run this maintenance on the last such day in the selected months, for example, every April, August, and December, to run the maintenance on the last Wednesday that month.

With all these recurring maintenance modes, it is possible to create nearly any scenario—one thing that might be missing is the ability to run monthly maintenance on the last day of every month.

So, the benefit of having this sort of a double configuration, that is, this overlap between the main period and the sub-periods, is that we can have recurring maintenance that starts at some point in the future and then stops at some point later completely automatically—we don't have to remember to add and remove it on a specific date.