The Black Bay GMT Date Wheel Problem Tudor Never Announced

Most of this series is about separating real faults from misunderstood normal behaviour. This post is the exception.

The early Black Bay GMT has a genuine, well-documented date wheel defect. It affected watches from the 2018 launch through roughly 2020 or 2021. Tudor revised the movement twice, and has repaired affected watches free of charge — including, in documented cases, after the warranty had expired.

Tudor has never publicly acknowledged any of this. There is no recall, no service bulletin, no statement. Tudor doesn't publish technical bulletins to consumers at all, so there was never going to be one.

If you own an early BB GMT, you should know about this.

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The problem

The symptoms are specific:

• The date advances early — sometimes hours before midnight.
• The date advances by half a day, or a day and a half.
• The date sticks halfway between two numerals in the window and stays there.

That last one is the signature. A numeral parked half-in, half-out of the window, refusing to complete its change.

The affected movement is the MT5652 in reference 79830RB. Production dates are the frustrating part: it appeared unpredictably across batches. Some owners of 2019 and 2020 watches never saw it. Others had 2020 watches develop the fault after eighteen months of normal use.

What we can say with reasonable confidence:

• Tudor issued two technical revisions of the MT5652. Version 2 is the one fitted to the Black Bay Pro, and it's interchangeable with the earlier variant.
• The issue is generally considered resolved by late 2021 / early 2022, with a couple of unconfirmed reports on later movements.
• Worn & Wound's owner review — the most reputable source on this — describes it as affecting "a handful of the early 'first-gen' watches from 2018/2019," fixed "mid-way through 2020."
• Millenary Watches reports that authorised dealers said Tudor temporarily halted production early on because of it. That claim traces to a single unsourced sentence in one article, so treat it as unconfirmed rather than established.

Note the scale carefully: "a handful of early watches," not "every BB GMT." This was never a defect that affected the whole production run.

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How to self-test

First — rule out the thing that isn't a fault

Before you diagnose anything, understand how this watch is supposed to work, because a large share of "my GMT date is broken" reports are actually owners fighting the design.

The Black Bay GMT has no independent date quickset. There is no crown position that just advances the date. The date is advanced by rolling the local hour hand past midnight.

Tudor's crown positions on this watch:

Crown position	What it sets
Fully unscrewed, last notch	Reference time — the 24-hour hand and the minute hand together
One notch out	Local time — the hour hand jumps in one-hour increments, and takes the date with it
(Bezel)	A third time zone, offset from the 24-hour hand

This is a true "traveller's" or "flyer" GMT — the local hour hand moves independently, which is exactly what you want when you land somewhere. But it means:

• "The date won't set" is often just someone looking for a quickset that doesn't exist.
• "The date changed and I didn't touch it" is often someone adjusting local time across midnight.

Neither is a fault. Work out which crown position you were in.

The actual test

1. Using the local hour hand (crown one notch out), set the watch to about 11:50 pm.
2. Watch the date window as midnight arrives.

Normal for an MT calibre: the date snaps over instantaneously — well under a second. MT date calibres change instantaneously in practice, and Tudor's own movement page for the MT5612 describes an "instant date display." There is no gradual creep by design.

Abnormal:

• Any slow crawl or gradual transition
• Changing noticeably before midnight
• Advancing by more than one date
• A numeral that stops halfway and stays there

Run it twice on different nights before concluding anything, and photograph the half-stuck date if you get one — you'll want the evidence.

While you're at it

Check the date is fully centred in the window after a completed change, looking straight down through the crystal. Photos taken at an angle are the single biggest source of false alarms about alignment. A numeral permanently sitting slightly off-centre is a different (and much more minor) issue than one that fails to complete its change.

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The solution

This is a warranty claim, and you should press it even if you think you're out of warranty.

Inside warranty: straightforward. Take it to your AD or a Tudor service centre. Describe the symptom precisely — "the date sticks halfway between numerals" is much better than "the date is weird."

Outside warranty: still ask. There are at least two documented cases of Tudor performing this repair as a goodwill gesture after the guarantee had expired. Worth understanding the detail: both were 2018-era watches, which carried Tudor's then-current two-year guarantee rather than today's five-year one. So nobody has yet documented a goodwill repair beyond five years — but the precedent for out-of-warranty goodwill on this specific fault is real, and it's circumstantial evidence Tudor treats it internally as a known defect.

Go in politely, describe the symptom, and mention it's a known issue with early 79830RB movements. Some owners have been refused, so it isn't automatic. The worst outcome is being told no.

What the repair actually is: whole-movement replacement, not component repair. Tudor swaps the MT5652 for a revised unit rather than fixing the date wheel. Some owners object to this because the movement serial number changes, breaking the link to the original COSC-certified movement — worth knowing before you send it, though there isn't really an alternative.

Turnaround: reported anywhere from eight weeks to about three months. Plan accordingly.

One documented failure case: one owner reports the fault returning after repair — three times. "After sending it to Rolex three times for repairs, the issue came back again each time." That's a single case and not the norm, but if yours comes back and does it again, you have precedent for escalating rather than accepting a fourth attempt. One owner got a full watch swap from his AD instead of a repair.

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If you're buying a used Black Bay GMT

• Ask when it was made. Watches from roughly 2022 onward have the revised movement.
• Ask whether the movement has been replaced, and if so, when and why. A service-replaced movement in an early watch is arguably better — it means the revised unit is in there.
• Test the date change before you buy if you possibly can, or negotiate a return window that lets you.
• The Black Bay Pro shipped with the version 2 movement from the start.

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Some perspective

It's worth saying that the Black Bay GMT is otherwise very well regarded, and this fault didn't affect every watch by any stretch. Plenty of 2018 and 2019 examples have run flawlessly for years.

But Tudor's handling of it — quietly revising the movement twice, quietly fixing affected watches, and never saying a word publicly — is the reason so many owners spent months wondering whether their watch was uniquely unlucky. It wasn't. If yours does this, it's a known defect with a known fix, and Tudor has paid for it in most reported cases, though not all.

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Sources: Millenary Watches — Tudor GMT date wheel issue · Worn & Wound — Owner's review: Tudor Black Bay GMT · Beyond the Dial — A second look at the Tudor Black Bay GMT · Rolex Forums — GMT date wheel issue query · Rolex Forums — Date change issue is back · Tudor — How to use the GMT function