How to get First Half and Second Half option in the Absence duration

Summary:

Hello all, As per the requirement we need to get the  First Half and Second Half option in the Absence duration drop down. Can anyone suggest me how to achieve this.

Content (required):

As shown in the screenshot, we need to get First Half and Second Half option.

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):