If you're shopping for a Seiko mod, you'll see "NH35" and "NH36" everywhere. They're the two most common movements in the modding world, and they're almost the same. Here's what you need to know.
The short answer
The NH35 shows the date. The NH36 shows the day and the date. Everything else is essentially the same.
What they have in common
- Automatic winding — a rotor winds the mainspring as you wear it. No battery.
- Hand-winding — you can wind it with the crown to get it started.
- Hacking seconds — the seconds hand stops when you pull the crown out, so you can set the time to the second.
- 24 jewels
- 21,600 beats per hour — that's the smooth sweep of the seconds hand.
- About 41 hours of power reserve — take it off Friday night and it may still be running Saturday afternoon.
NH35 vs NH36 side by side
| NH35 | NH36 | |
|---|---|---|
| Display | Time + date | Time + day + date |
| Winding | Automatic + hand-wind | Automatic + hand-wind |
| Hacking | Yes | Yes |
| Frequency | 21,600 bph | 21,600 bph |
| Power reserve | ~41 hours | ~41 hours |
Which one should you get?
It comes down to the dial you want. A clean date-at-3 layout, like a fluted-bezel date watch or an octagon sports watch, typically uses an NH35-style movement. If you want the day spelled out at 12 o'clock, like on a day-date watch, you want an NH36.
Other NH variants you'll see
- NH34 — adds a GMT hand for tracking a second time zone. It's what makes a GMT mod a true GMT.
- NH38 — no date at all, for a perfectly symmetrical dial.
How to care for an NH movement
- Wear it daily and it'll keep itself wound.
- If it stops, give the crown 20–30 turns, then set the time.
- Don't change the date between roughly 9pm and 3am, when the date wheel is engaged.
- Keep it away from strong magnets, which can affect timekeeping.
Chronos Mods watches use a different self-winding automatic movement, not a Seiko NH-series caliber, and every one comes with a 2-year warranty. Shop all our watch mods.