If you are using Google Calendar, you don't need to do anything in particular, and if you have the same account, it will be migrated automatically.
LOCAL calendars
1. Select "Data Backup and Restore" in the settings screen to output the backup data, and then transfer the backup data to your new device by email or your preferred method.
2. On a new device, download the backup data you just transferred and save it on the device.
3. On a new device, download and launch this app and tap "Restore Backup" button from "Data Backup and Restore" on the settings screen to select the backup data that has been transferred.
That's all there is to it. If it doesn't work, please contact us from the top right button.