Samsung
Change Calendar View auf Samsung
The Samsung Calendar app defaults to month view every time it starts, regardless of which layout you used last. This happens because the app stores a single display preference that only changes once you actively select a different view from the menu.
To switch between year, month, week and day layouts, open Calendar, then open the Menu and choose Year, Month, Week or Day.
The app saves this choice locally and reopens in the same view the next time you launch it, until you change it again or the app data gets reset.
If the calendar keeps falling back to month view after every restart, check whether a recent system update or a cleared app cache reset your saved preferences. In that case, just repeat the selection once and the setting stays until you change it manually again.