The Tudor Black Bay GMT and Longines Spirit Zulu Time both offer automatic GMT movements with chronometer certification, but they differ in size choices, bezel materials, water-resistance ratings and the way the Tudor’s second-time-zone hand is set. The cited Tudor reference 79830RB is 41 mm; Longines offers the Spirit Zulu Time in 39 mm and 42 mm versions. Choose by the exact configuration that fits your wrist and priorities—not by the name alone.
At a glance: the key differences
| Feature | Tudor Black Bay GMT, ref. 79830RB | Longines Spirit Zulu Time |
|---|---|---|
| Case size | 41 mm, according to Tudor’s reference specification sheet | 39 mm or 42 mm in the official US collection |
| Bezel | Bidirectional 24-hour bezel with burgundy-and-blue anodized aluminum insert | Bidirectional bezel with ceramic insert on the cited steel references |
| Water resistance | 200 m, per Tudor’s reference sheet | 10 bar on the cited 39 mm and 42 mm US listings |
| Power reserve | Approximately 70 hours, per Tudor | Up to 72 hours, per Longines |
| Second-time-zone display | Dedicated 24-hour hand and jumping local hour hand | Dedicated 24-hour hand for the second zone; the product pages list GMT/date |
| Price evidence | A current US price for this exact reference was not established | Official US pages accessed showed steel-and-ceramic examples at $3,450 or $3,550; price depends on configuration |
These are manufacturer specifications and displayed US prices, not independent test results. Case diameter alone does not establish how a watch wears, and the configurations listed by each brand can differ in dial, bracelet or strap.
| # | Preview | Product | Price | |
|---|---|---|---|---|
| 1 |
|
Tudor Heritage Black Bay GMT Stainless Steel Automatic Mens Watch M79830RB-0001 | $4,650.00 | Buy on Amazon |
| 2 |
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Tudor GMT 58 Black Bay | $5,449.98 | Buy on Amazon |
| 3 |
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TUDOR Black Bay 58 GMT | $5,550.00 | Buy on Amazon |
| 4 |
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Tudor Black Bay Automatic Black Dial GMT Pepsi Bezel Men's Watch 79830RB-0002 | $4,900.00 | Buy on Amazon |
| 5 |
|
Tudor Black Bay Automatic Chronometer Black Dial Men's Watch M79833MN-0001 | $7,499.99 | Buy on Amazon |
How do the two watches track a second time zone?
Tudor: jumping local hour and 24-hour bezel
Tudor’s specification sheet for reference 79830RB identifies a jumping hour hand for the second time zone, a 24-hour hand, and an instantaneous date synchronized with the jumping hour. In practical terms, the jumping hour lets the wearer adjust the local hour in one-hour increments while the 24-hour hand continues to indicate the other time zone. The bidirectional bezel provides a further 24-hour reference. Tudor also lists stop-seconds, which lets the seconds hand stop when the crown is pulled for time setting. See the Tudor Black Bay GMT specification sheet.
Longines: dedicated 24-hour hand
Longines’ product pages identify GMT and date functions. Its general GMT explainer describes the familiar layout: standard hour and minute hands show local time, while a dedicated 24-hour hand indicates a second zone. That is a general description of GMT displays, not a model-specific setting procedure; consult the instructions for the exact calibre and reference before changing the time. See the Longines GMT explainer.
#1 Best Overall
- 41mm steel case with polished and satin finish
- Bidirectional rotatable bezel in steel with 24-hour graduated anodised aluminium disc
- Self-winding mechanical movement with 70 hour power reserve
Which size and configuration should you choose?
Longines gives you a smaller and a larger option
The official Longines US collection includes Spirit Zulu Time models in 39 mm and 42 mm. The cited 39 mm reference, L3.802.4.53.2, is listed with a leather strap; the cited 42 mm reference, L3.812.4.50.6, has a black matte dial and steel bracelet. Compare the exact reference you intend to buy, since strap, bracelet and dial options vary. The 39 mm listing and 42 mm listing establish those configurations.
Tudor’s cited reference is 41 mm
The Tudor Black Bay GMT sheet describes reference 79830RB with a 41 mm stainless-steel case. Its documentation describes steel-bracelet and fabric or leather options. The specification sheet is reference-specific and dates from the 2023 era; it does not confirm that every detail or configuration applies to a current listing. Check the current reference and configuration before purchasing. The 2023-era Tudor specification sheet and an earlier 2018 Tudor sheet cover the cited reference.
Rank #2
- Tudor Black Bay 58 GMT "Coke" Automatic 39mm Black Dial Men's Watch M7939G1A0NRU-0001
Try the exact watch on the bracelet or strap you plan to wear. Diameter is only one part of fit, and the available specifications do not establish how either model will feel on a particular wrist.
Bezel materials, water resistance and movement specifications
Bezel material is a preference, not a proven durability ranking
The cited Tudor uses a burgundy-and-blue anodized aluminum 24-hour bezel insert; the cited Longines steel-and-ceramic references use ceramic inserts. These are clear differences in material and appearance, but the specifications do not support a comparative claim about which bezel is more durable or scratch-resistant.
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Rank #3
- Tudor Black Bay 58 GMT "Coke" Automatic Black Dial Men's Watch M7939G1A0NRU-0002
Water-resistance ratings are not identical
Tudor rates reference 79830RB to 200 m, while Longines lists 10 bar for the cited 39 mm and 42 mm models. These are the manufacturers’ ratings; they are not independent water tests or a guarantee of suitability for a particular activity. Follow the brand’s guidance for the exact watch and its crown and seals.
Both brands describe chronometer-certified movements
Tudor’s sheet names Manufacture Calibre MT5652, COSC certification and a silicon balance spring, with approximately 70 hours of power reserve. Longines says the cited Spirit Zulu Time calibre has a monocrystalline silicon balance spring and is COSC-certified, with up to 72 hours of reserve. Those reserve figures are manufacturer specifications, not measured results from a comparative test. Longines’ Spirit Zulu Time overview describes its exclusive calibres as silicon-equipped and COSC-certified.
Rank #4
- Tudor Black Bay Automatic Black Dial GMT Pepsi Bezel Men's Watch 79830RB-0002
What do the cited US prices establish?
The official Longines US collection showed steel-and-ceramic examples at $3,450 or $3,550 on the pages accessed; the cited 42 mm reference page displayed $3,550. These are snapshots for particular US configurations, not a single price for every Spirit Zulu Time. The collection also lists other material options at higher prices. Check the exact reference and current US listing at the Longines US collection before comparing offers.
A current US price for Tudor reference 79830RB was not established. Tudor’s specification PDF includes Swiss pricing, but that is a different market and date context, so it is not a like-for-like US comparison. Verify a current local price for the exact Tudor configuration before deciding on value.
Best Value
- Tudor Black Bay GMT S&G Automatic Chronometer Black Dial Men's Watch M79833MN-0001
Which GMT watch should you buy?
- Choose the Longines Spirit Zulu Time if you want a choice between 39 mm and 42 mm, prefer a ceramic bezel insert, or are comparing one of the currently displayed US steel-and-ceramic configurations. Confirm the reference, strap or bracelet, and live price.
- Choose the Tudor Black Bay GMT if you want the cited 41 mm reference’s jumping local hour, burgundy-and-blue aluminum bezel, or its stated 200 m water-resistance rating. Confirm the current listing and price because the cited specifications are reference-specific and older.
- Try both before choosing if fit is the deciding factor. The available case diameters do not substitute for trying the precise case and strap or bracelet on your wrist.
For a fair purchase comparison, match region and configuration, then check the exact reference, current price and retailer availability. Neither brand’s specifications alone establish a universal winner.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
