Notion Calendar

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Build me a calendar that replaces Cron: fast, keyboard-driven, and honest about time zones.

STACK
- A native application, or a PWA if the menu bar matters less than the effort
- SQLite on device as the local mirror
- CalDAV as the protocol, plus the major providers' own APIs. Do not invent a sync protocol
- Caddy in front only if you add an availability-sharing page

THE LOCAL MIRROR, WHICH IS WHY IT FEELS FAST
- Every event held locally and every view rendered from it, so opening the calendar is instant with no request at all
- Sync incrementally in the background with the provider's token, plus a full reconcile on a schedule because incremental sync drifts
- Changes apply locally first and are queued outward. The interface never waits for a round trip

TIME, WHICH IS WHERE THESE GO WRONG
- Every event stored as an instant with its named zone. Never an offset
- **All-day events are dates, not midnight instants** — the classic bug, and the one that makes a birthday land on the wrong day for anybody east of you
- Recurrence rules expanded properly, with exceptions and moved instances. A wrongly expanded weekly meeting is wrong for a year
- Both daylight-saving transitions in the test suite, plus a zone whose rules changed
- A second zone shown alongside your own, permanently, if you work across one. That single column prevents more scheduling mistakes than any feature

THE KEYBOARD
- Create, edit, move, delete and navigate without a pointer. Typing a sentence to create an event — 'lunch with Anna tuesday 1pm' — parsed on the device, instantly
- **The parse shown as correctable chips before saving**, never applied silently. Right most of the time is worse than useless if you have to verify every entry
- A command palette for everything else, because that is how anything not bound to a key gets found

MANY CALENDARS AT ONCE
- Several accounts overlaid, each with a colour, toggled individually
- Calendar sets: a named group switched in one action, so work and personal are separate contexts rather than a wall of colour
- Read-only subscribed feeds treated as first-class, since that is how a shared team calendar usually arrives

SHARING AVAILABILITY, WHICH IS THE FEATURE PEOPLE LOVE
- Select some free slots and produce **a block of text somebody can paste into a reply**, with the times in their zone as well as yours
- Or a link that lets them pick, which needs a small server: the slots, a picker, and a booking that writes the event
- Either way the slots are computed from real availability at the moment of asking, not from a saved list that goes stale

THE MENU BAR
- What is next, how long until it, and a click to join. That is where the application actually lives for most of the day
- A notification a few minutes before, and the join link right there — the small thing that stops people being late

OPERATIONS
- Local first, working entirely offline
- If there is a sharing server: .env with DATABASE_PATH, BASE_URL, SESSION_SECRET, provider credentials; migrations on boot; nightly backup
- No analytics. A calendar knows where you are going and with whom

WHAT MATTERS MOST
The local mirror and all-day events as dates. The first is the whole feel of the application; the second is the bug that makes people quietly stop trusting it.