I can't find any calendar that is offline and cross-plat across Win+Android+Linux (goal: leave Google Cal) Edit: Server-less

Edit: I seek a server-less solution.

The only thing I can see is Linwood Flow but it looks like it's a really, really long way off before becoming a primary calendar app.

If it could just store all calendar content in 1 local file, then that could be so easily auto-synced across devices with [email protected]. Does anyone have any leads?