still to be verified
In one line
A 2824-2 with a day disc on top: same diameter, same frequency, the same 38 hours, and 0.45 mm more height. It ended up outlasting its famous sibling in ETA's catalogue.
First things first: day at three and day at twelve are not the same calibre
ETA makes two automatics with day and date, and buyers confuse them constantly. They stand the same height, carry the same 25 jewels and give the same 38 hours. What differs is the diameter and where the day sits — and that you can read straight off the dial.
Day spelled out in an arc at 12 → 2834-2, Ø 29.00 mm
Both stand 5.05 mm tall.
The difference matters because the cases are not interchangeable. The 2834-2 wants three and a half millimetres more room across, so you cannot swap one for the other — you change the watch.
ETA's own paperwork spells it out. One technical booklet covers the 2801-2, 2804-2, 2824-2, 2834-2 and 2836-2, and in the interchangeability list the day indicator carries two separate part numbers: one for the arc-shaped aperture at 12, one for the rectangular window at 3.
2836-2 against 2824-2: what knowing the day costs you
Almost everything here is identical, which is the point. The interest lies in the two rows where it isn't.
| ETA 2836-2 | ETA 2824-2 | |
|---|---|---|
| Day of the week | Yes | No |
| Height | 5.05 mm | 4.60 mm |
| Diameter | 25.60 mm | 25.60 mm |
| Jewels | 25 | 25 |
| Power reserve | 38 hours | 38 hours |
| Automatic module | The same part | The same part |
| In ETA's open catalogue | Stayed on sale | Withdrawn after 2021 |
Those extra 0.45 mm are the day disc and the works that drive it. On a slim dress watch, that can be the difference between slipping under a shirt cuff and catching on it.
And “the same part” is not a figure of speech. In ETA's spare-parts list, the rotor, the ball bearing and the reversing wheels of the 2836-2 carry the same reference numbers as those of the 2824-2 and the 2834-2. Literally the same components.
Where it comes from
Say it plainly at the start: the 2836-2 has no story of its own, because it is not a separate calibre. It is one of five versions of the same machine, and ETA documents all five in a single technical booklet — they share mainplate, bridges, going train and balance.
The 11½-line family runs from the 2801-2 — hand-wound, 3.35 mm thick, 17 jewels — up to the 2836-2 with day and date. In between sit the 2804-2, hand-wound with date, and the 2824-2, automatic with date. The 2834-2 is the same layout stretched to 29 mm so the day can go up at twelve.
The ending has a twist. As ETA thinned the family out of its open catalogue, the ones to go were the best sellers — the 2801-2, the 2824-2 and the 2826-2 — while the 2804-2, the 2834-2 and the 2836-2 stayed on sale. The brother with the day outlived the famous one.
Two things almost nobody knows
- The disc carries the week twice over. An ETA day disc has fourteen positions: seven days in one language and seven in another, interleaved. The day works step two at a time, skipping the language you are not using. If your watch wakes up one morning in French, it isn't broken — nudge it one position on with the crown and it is back in step.
- There was a service 2836-2 in English and Hebrew. The Marathon JDD, a 46 mm watch built for military units, runs this calibre with an English-Hebrew disc in the version made for the Israeli YAMAM unit. Forty-six millimetres of case around a movement of twenty-five and a half.
Technical data
| Type | Automatic with day and date |
|---|---|
| Family | ETA's 11½-line family (2801-2 / 2804-2 / 2824-2 / 2834-2 / 2836-2) |
| Diameter | 25.60 mm (11½ lines) |
| Height | 5.05 mm |
| Jewels | 25 |
| Frequency | 28,800 vph (4 Hz) |
| Lift angle | 50° |
| Power reserve | 38 hours (ETA official data sheet) |
| Day window | Horizontal rectangle at 3, next to the date |
| Regulation | Etachron |
| Other functions | Manual winding, hacking seconds, quickset day and date |
What a watchmaker checks before buying one
On a 2824-2, the rotor is what usually goes. On a 2836-2, it's the day.
The test is simple. Set the watch to half past eleven at night and let it run through midnight. The day should jump the whole way in one go and settle centred in the window. A day that stalls halfway between two words, or needs a nudge from the crown to finish falling, has a tired double flexible spring or a worn day-indicator jumper.
The golden rule for the whole family: never quickset the day or the date between nine at night and three in the morning. In that window the day and date works are already engaged for the jump, and forcing them from the crown breaks real parts.
The good news is the disc itself. Scratched, yellowed or printed in a language you don't want, it is a loose part, cheap, and available in dozens of combinations. Nobody should walk away from a watch over that.
Watches that used it
- Tissot Heritage Visodate
- Marathon JDD — 46 mm, in military issue
- Fortis, Ball, Oris and Hamilton, in their day-date models
- Tudor Prince Date+Day — careful: this one takes the 2834-2, the 29 mm version
The same movement without the day, and 0.45 mm slimmer, is the calibre 2824-2.