You can just use the Calendar apps on your phone and/or laptop. Etar is a good option for Android.
If you want synchronisation, you will either have to set up a calDAV based server yourself, or use someone else’s. I use Nextcloud, and it synchronises many things, like calendar, contacts, tasks etc., using DAV protocol.
There are some public Nextcloud servers with server-side encryption that you can go for. Setting up your Nextcloud just for calender would be overkill. You may want to take a look at some awesome-selfhosted list, if you are into self-hosting.