In My Hours you can easily track absences. To enable this, create a new project and title it ‘Absences’. Add all users to this project.
Then add all types of absences (sick leave, annual leave, maternity leave, national holiday…) as tasks to the 'Absences' project.
Then your users can simply put in hours for the ‘Absences’ project (with the correct task/type of absence) when they are missing from work.
You will be able to view all absences in the Detailed report, which you can filter for the ‘Absences’ project and a specific team member in a selected time period.