Calendar Pro
One click saves everything in Calendar - every calendar, event, day note, template, category, linked calendar and your settings - in one file. Restore it on this PC or a new one: you see what's in it first, then merge it with what you have or replace everything. Calendar keeps a copy of what you had, so a restore can be undone. Part of Calendar Pro.

··· > Print & export > Backup and restore > Back up now. The .json file goes to your Downloads.
Copy it to a USB stick, a network drive or your cloud folder. It has your linked calendars' private addresses in it.
Open a backup file… shows its events, calendars and notes next to yours. Choose Merge or Replace.
Calendar saves what you had first. Undo the last restore puts it back.
Backup and restore help has every option in detail.
Part of Calendar Pro. Calendar is free. Calendar Pro is a one-off £5.99 upgrade inside the Windows app, bought through the Microsoft Store - no subscription, no account. Try it free for 7 days.
Not yet - backups are saved when you click Back up now. Turn on the weekly reminder and Calendar tells you when it's been a week.
No. Events already in your calendar (same title, date and times) are skipped, and calendars are matched by name.
In your Downloads folder, named metre2-calendar-backup and the date.

Day, Week, Timeline, Month and Agenda - drag to reschedule, week numbers and UK bank holidays.

Tag events by project, filter to one, and log actual hours against planned.

Notes for every day, exported as a formatted site diary for any date range.

Windows notifications before your events, even when Calendar is closed.

Day, week, month and year wall planners in three styles - print or PDF.

Every event for a project, planned against logged hours, with CSV export.

Diary entries, weekly update emails and project summaries - private, on your PC.

Midnight, Graphite, Forest, Plum, Paper and Ocean.

All twelve months at once, with event dots - click a day to open it.

Bank holidays for Scotland, Northern Ireland and Ireland, and the clock changes.

Weekly and monthly timesheets from your hours, and an invoice from them.
Calendar is free, in your browser and on Windows. Calendar Pro is a one-off £5.99 in the Windows app, with a free 7-day trial.