To set up a scenario for regular maintenance, the first event should take place after 1 year, and after that, it is a regular cycle of 6 months, you have to use the maintenance package offset parameter to map this in the system. The maintenance package offset is used to define the time interval between the start of the maintenance plan and the first call date of the maintenance package1. A maintenance package is a set of data that defines the frequency and scope of the maintenance tasks2.
For example, if you want to create a maintenance plan with two maintenance packages, one for annual inspection and one for semi-annual inspection, you can use the following settings:
Maintenance package 1: Cycle length = 12 months, Offset = 0 months, Scheduling indicator = Time-based Maintenance package 2: Cycle length = 6 months, Offset = 12 months, Scheduling indicator = Time-based This means that the first maintenance package will be called at the start of the maintenance plan, and then every 12 months thereafter. The second maintenance package will be called after 12 months from the start of the maintenance plan, and then every 6 months thereafter.
The other parameters that are not relevant for this scenario are:
Package hierarchy: This is used to define the relationship between different maintenance packages within a maintenance plan. It allows you to create nested or parallel maintenance packages that are dependent on each other3.
Scheduling indicator: This is used to define the type of scheduling for the maintenance package, such as time-based, performance-based, or condition-based4.
Cycle modification factor: This is used to modify the cycle length of the maintenance package by a certain percentage or factor5.

Explanation
The action log is a function that allows you to view the changes that were made to fields during the processing of an order or a piece of equipment. The action log shows you the date, time, user, sub-object, field name, old value, and new value of each change. To enable entries in the action log of a piece of equipment, you need to activate the change documents for the equipment category. The equipment category is a classification of equipment that determines the data that can be maintained for the equipment. The change documents are records of the changes that are made to the data of the equipment. You can activate the change documents for the equipment category in the Customizing for Technical Objects under Equipment Define Equipment Categories . You do not need to define history related fields in the usage period customizing, as this is only relevant for the equipment history. The equipment history is a function that allows you to view the usage periods of the equipment, such as the installation, removal, or transfer dates. The history related fields are fields that are relevant for the equipment history, such as the functional location, the maintenance plant, or the cost center. You can define the history related fields in the Customizing for Technical Objects under Equipment Define History-Related Fields for Usage Periods . You do not need to define or activate the change documents for the equipment reference category, as this is only relevant for the equipment reference. The equipment reference is a function that allows you to link a piece of equipment to another object, such as a material, a serial number, or a document. The equipment reference category is a classification of equipment references that determines the data that can be maintained for the equipment reference. You can define the equipment reference category in the Customizing for Technical Objects under Equipment Define Equipment Reference Categories . You can activate the change documents for the equipment reference category in the Customizing for Technical Objects under Equipment Define Change Documents for Equipment Reference Categories . References:
Display of the Action Log, section "Use"
Equipment Categories, section "Change Documents"
History-Related Fields for Usage Periods, section "History-Related Fields" Equipment Reference Categories, section "Change Documents"