An example morning, afternoon, night and off rotation in one calendar.
Start with a reliable reference day
A repeating calendar is only as accurate as its anchor date. Use a day from the official rota whose position in the cycle is known. Avoid guessing from memory when the pattern contains similar consecutive shifts.
Keep the pattern separate from exceptions
The cycle describes the normal rotation. Overtime, swapped shifts, leave and training are exceptions. Recording them separately keeps future months correct and makes a backup easier to understand.
Check the result before using it
Compare several dates at the beginning and end of the displayed period with the employer rota. If every date is shifted in the same way, correct the anchor. If only one date differs, treat it as an exception.
Use exports as copies, not as the source of truth
ICS, CSV, PNG and print are useful for your calendar, family planning and archives. The official schedule and later employer changes remain decisive.