Seiko NH35 vs NH36: What's the Difference? (Full Comparison)
The Seiko NH35 and NH36 power a huge share of affordable automatic watches, from the Seiko 5 Sports range to hundreds of microbrand divers. They look nearly identical on paper, so which one is in your watch, and does it matter? Here is a clear breakdown.
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The short answer
The NH35 shows the date only. The NH36 shows the day and the date. Mechanically they are the same movement: same beat rate, same jewels, same power reserve, same accuracy specification. The NH36 simply adds a day-wheel complication.
Side-by-side specifications
| Specification | NH35 (NH35A) | NH36 (NH36A) |
|---|---|---|
| Display | Hours, minutes, seconds, date | Hours, minutes, seconds, day, date |
| Beat rate | 21,600 vph (6 beats/sec) | 21,600 vph (6 beats/sec) |
| Jewels | 24 | 24 |
| Power reserve | about 41 hours | about 41 hours |
| Accuracy (Seiko spec) | -20 to +40 s/day | -20 to +40 s/day |
| Hand-winding | Yes | Yes |
| Hacking seconds | Yes | Yes |
| Diameter | 27.4 mm | 29.4 mm (with day wheel) |
| Thickness | 5.32 mm | 5.32 mm |
| Crown positions | 3 (wind, date, time) | 3 (wind, day/date, time) |
NH35/NH36 vs 4R35/4R36: are they the same?
Yes, essentially. 4R35 and 4R36 are the names Seiko uses when the movement goes into Seiko-branded watches. NH35 and NH36 are the names used when Seiko Instruments (SII / TMI) sells the same movement to other brands. Finishing and the rotor engraving can differ, but the design and performance are the same.
How to tell which one your watch has
- Look at the dial: a day window (often showing "MON", "TUE", sometimes in two languages) means NH36/4R36. Just a date means NH35/4R35.
- Check the case back or the spec sheet. Many microbrands list the caliber.
- Crown at 4 o'clock? Some watches place the crown at 4. The movement is still an NH35/NH36, just with the dial rotated or a modified date wheel.
How to set the day on an NH36
- Pull the crown to the middle position.
- Turn it one way to change the date, the other way to change the day (direction depends on the watch, usually counter-clockwise for date and clockwise for day on Seiko).
- Many NH36 day wheels are bilingual (for example English and another language). Cycle past the language you don't want.
- Avoid changing the day or date between about 9 pm and 3 am, when the calendar gears are engaged (see the date danger zone).
NH35 vs NH36: which should you choose?
- Choose an NH35 if you prefer a cleaner, more symmetrical dial. Many divers and field watches use it for that reason.
- Choose an NH36 if you like the classic "day-date" look and the practicality of seeing the weekday at a glance.
Reliability, service cost and accuracy are the same. The choice is about dial design.
Why are these movements so popular?
- Robust: simple, proven design with good shock protection.
- Affordable: they keep watch prices low.
- Easy to service or replace: watchmakers know them well, and a complete replacement movement is often cheaper than a full service.
- Modding-friendly: they are the base of the huge Seiko modding hobby, with countless compatible dials, hands and cases.
Common questions
Is the NH35 a good movement?
Yes, for the price it is one of the best. It is not finished or regulated like a Swiss chronometer, but it is durable, easy to service and hand-winds and hacks, which older Seiko movements like the 7S26 did not.
Can you replace an NH35 with an NH36?
It is possible, but the NH36's day wheel makes it slightly wider and needs a dial with a day window. For a date-only dial, stick to an NH35, or use an NH36 with its day wheel removed (a common modder's trick).
What is the difference between NH35 and NH35A?
None in practice. "A" is simply part of the official reference used by the supplier.
How long does an NH35 last?
With reasonable care, many run for 10+ years. Service intervals of around 5–7 years are a sensible guideline if accuracy or power reserve drops.
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