That kind of depends on your definition of shared calendar. If you have granted permissions on the calendar via Outlook, PowerShell or the Share button, the entire range is shared. If you have Published the calendar, you can select a specific timeframe.
I tried to publish a test calendar to be shared and I didn't see any option for a specific date range to share. What I want to do is to share just our 2019 department calendar. I don't want people seeing the 2020 yet.