Yes, you can. The Android version of Smart Planner stores your events, ToDos, notes, and diary entries inside the app, so you can start adding events right after installing it without linking Google Calendar. Calendar access permission is not required either.
Turn on "Link Google Calendar" only if you also want to see the events saved in your Google Calendar in this app.
Turning Link Google Calendar on or off
- In the tutorial shown at first launch (the "Final settings" screen), you can choose whether to turn on "Link Google Calendar". It is perfectly fine to start with it turned off
- To change it later, go to the settings screen and tap "Calendar Settings" → "Link Google Calendar"
- When you turn it on, the app asks for permission to access your calendar. If you choose "Don't allow", Google Calendar events are not shown (you can change this later in your device's "Settings" app → "Apps" → "Smart Planner" → "Permissions" → "Calendar")
※ Turning the link off never deletes the events you created in this app (events in the "Local calendar").