Using Classic Outlook on Windows for personal email, calendar, and contact management
You should be able to set the hours using the new Work Hours and Location (File, Options, Calendar, Work hours and location), Set your work hours and location in Outlook - Microsoft Support.
This feature is now at Current Channel and Monthly Enterprise Channel at builds Version 2503 Build 18623.20000+. As that version advances to the other channels, it will get the feature. If you do not have the feature yet use OWA or New Outlook to set the Work Hours. After you set the hours in OWA restart classic Outlook to pick up the change.