while the client is online Calendar integration with .ics or CalDav works quite well with Thunderbird/Lighting or Evolution.

TB/ Lightning and Evolution offer a function to make the calendar offline available.
But unfortunately in TB/Lightning in offline mode the calendar disappears completely if that function is enabled and in Evolution the calendar is still visible in offline mode but you can't edit that calendar.

So, is there any possibility to use and edit calendars with TB or Evolution while the client is offline and that changes that are made offline are synced next time the client goes online ?

Tanks for your help!