Tide Mark

Tide Mark is a small private timezone utility styled like a harbor port log. You set your home city as the HARBOR in Settings; every contact you add becomes a square port tile in a 2-column grid. Each tile shows a 3-letter airport-style code on a brass chip, the city name, the local time in big mono, and a small wave line tracing the contact's daylight hours with the current hour marked. The home screen reads like a navigator's chart: wave above, ports below.

THE TIDE CHART

Across the top sits a wide TIDE CHART -- a sinusoidal daylight curve of YOUR home day. Bars rise to noon and fall to midnight. Where the bar lights up in seafoam mint, that is a time when all your tracked ports are inside their own working hours. A small outline marks the current hour in your harbor. Below the wave, the longest overlap window is reported in plain numbers like "WINDOW 14:00 - 17:00".

THE PORT TILES

The body of the screen is a 2-column grid of square port tiles (not the single-column list used in most timezone apps). Each tile fits more information per pixel: brass code chip top-left, delta badge top-right (+8h / -5h / SAME), name and city label in the middle, big mono time block, and a stylised wave line at the bottom whose bars peak at the contact's noon. A small brass dot at the bottom-right marks a pinned port. Long-press a tile for the action sheet.

THE DROP-ANCHOR BUTTON

The action lives in the BOTTOM-LEFT corner of the screen as a round brass FAB (mirror of the typical bottom-right position). This is a deliberate layout swap so the dominant hand can reach it without crossing the screen, and so the planner controls live where the user naturally lands when scanning a port log from upper-right to lower-left. Tap it and a compose sheet pops up: name, city picker (115+ IANA cities plus raw UTC offsets), notes.

THE HARBOR VIEW TAB

The second bottom tab is a Harbor view -- every unique port you track, sorted by hour offset. Each row carries the city name (or your custom label), the IANA id, day-shift hint (same day / next day / prev day), all contact names in that port, the delta badge, and the big local time. A + ADD CITY pill top-right opens the same searchable picker. Long-press a row to remove all contacts in that port.

THE EDITOR

Tap a tile to open the editor: tall colored header band with the contact name, role chips, city picker, free notes field. Save, archive, pin, or delete from a row of action buttons at the top.

SETTINGS

Pick your HARBOR city from the same searchable picker. Add a custom display label (any text). Toggle 24-hour or 12-hour clock format. Tune the working window to any whole hour 0-23 using +/- steppers or by tapping a number and typing.

PRIVACY

Tide Mark keeps every port on your device. No sign-in, no cloud sync, no analytics, no ad SDK. The store is encrypted at rest with a key that lives in the Android Keystore. No network permissions are requested. If you uninstall the app, the data goes with it.

WHO IT IS FOR

- distributed engineering and product teams scheduling syncs across continents
- founders running calls with offices in different regions
- account managers and recruiters coordinating across timezones
- freelancers juggling clients across the EU, the Americas, and Asia
- anyone with family or close friends in another timezone who is tired of doing the hour math in their head

NO ACCOUNTS. NO CLOUD. NO ADS. JUST TIDES.