Half days in calendar

Hello,

Would it be possible to plan an evolution to manage half-days in the calendar ?
We use specific calendars for people working part-time (80%) - but we also have many people working 90% (4,5 days per week).
It would be great for exeample to :
- click once for changing the status to non-working
- click a second time to set as working half-day
- click a third time to set as working

Cheers!