Migrating a NC calendar and address book

I want to migrate my Nextcloud calendar and address book from the recent provider to a new hosting provider. The recent NC installation is running on www.old.tld, the new one will run at www.new.tld.

How do I achieve this at the easiest and most reliable way?

Since these infos are held in the database, you’d export your contacts and calendar(s) to their appropriate files and take the to the new instance. Simply go to the options button of each of your addressbooks/calendars and hit the three dots button - chose download.