Every device disagrees.
We settle it.

A few seconds of drift is a rounding error. A photo that should be at 14.2m lands at 14.0m. Nobody loses sleep.

A few minutes and the last photos from the dive fall outside the window. You get a partial match and wonder why six shots are missing. The shark was real. The photo just doesn't know it was part of a dive.

A timezone error is silent and total. Camera bought in Tokyo, never adjusted for Cairns. Every photo from the Great Barrier Reef sits one hour ahead of the dive. None of them match. They're not in the log. Critter ID never runs on them. They have no GPS. They have no depth. They're just photos now — disconnected from the dive that gave them context.

Deltas are recorded on every dive — from the original device timestamps, never from an overwrite. Corrections are computed fresh each time, so adjusting an offset updates the result everywhere automatically.

Serious divers often carry a second computer — different brand, different algorithm, set it and forget it. It disagreed with the primary computer when you bought it and it still disagrees now. That's fine.

DeepSix assigns it to the dive, records its clock offset, and notes that it contributed zero profile samples. The decompression obligation is on record. The wrong timestamp doesn't corrupt anything — it's offset-corrected and clearly labeled.

It showed up. That's enough.

Clock drift you notice. Timezone errors you don't — until you open the log and nothing matches.

A camera set to UTC+9 on a dive in UTC+10 puts every photo one hour after the dive ended. Not close. Gone. The shark photo sits in your library with no dive attached, no depth, no GPS. DeepSix never knew it was from a dive.

DeepSix tries to resolve timezone automatically before asking you to do anything. It works through four tiers: GPS coordinates on the dive entry resolve to an exact timezone polygon offline. If there's no dive GPS, the site coordinates are used instead. If there's no site GPS, a 70-country lookup table covers the common cases. If nothing else works, timezone is borrowed from a concurrent dive within the same 14-hour window — your buddy's Shearwater already resolved it.

When automation has enough information, it corrects silently. When it doesn't — liveaboard that crossed a boundary on day three, borrowed GoPro, camera that's been on Tokyo time since 2019 — DeepSix shows you the mismatch and lets you apply the fix manually per dive or per trip.

The resolved zone is also what you see. Every screen — the dive list, the detail page, photo tags — renders each dive in that dive's own local time zone, not your device's. A Sardinia morning dive reads as morning whether you're browsing from Cairns or Chicago. Even a site beyond territorial waters resolves to a sensible civil time zone instead of a raw nautical offset.

And when you download from a dive computer whose clock doesn't match your phone's, DeepSix says so: a non-blocking warning banner classifies the mismatch and offers to confirm the dive's time zone on the spot. It stays silent in the common everything-agrees case, and GPS only ever hints at a zone — it never applies one for you.

For dedicated dive cameras and Paralenz units, there's one more layer: DeepSix can scan your existing matched photos, detect a systematic offset between stored timestamps and what's in your library, and apply the correction retroactively across the whole trip. If enough photos cluster around a consistent error, it finds it.

If you've ever imported photos and had none of them match, timezone is almost certainly why.