We’ve talked before about concepts like Precision, Rate and Accuracy as factors affecting timekeeping, along with temperature, position and others.

Whilst I’m interested in what makes for good timekeeping (a better overarching term than “accuracy” in my opinion) I’m certainly not OCD about it. A quick check against the G-shock, RC clock or time.is and I’m good to go. I’ve never used a timegrapher or an app. Empirical observations and quick calculations will do.

Anyway, I’ve been wearing the Sealander for about 10 days now, and it will certainly be my only watch for the next 10 days or so.





It has always kept good time, but I’ve noticed patterns with this particular watch (and sometimes others): after a few days it settles down to very precise and accurate timekeeping, and the current rate is holding very steady at less than +1 s/d. I’ve been very impressed with the Sellita SW330-2 movement since I first got the watch. But it certainly seems to perform better after a few days of constant wear (only removed for the shower, jacuzzi, sauna and steam room).

I wonder what factors contribute to this? I’ve read that constant wear helps lubrication by moving the oils around. But I wonder also whether the constant positional variation helps, the continual winding, and the contact with a surface at skin temperature (I wear it when I’m asleep as well)?

As I said, I’ve noticed it to some extent with other watches, but it seems to be a noticeable feature of this one. It became apparent a few years ago when I started wearing just one watch on trips, and settled into my current pattern of wearing the same watch for days on end. If you are an habitual changer or rotator it’s likely you won’t have noticed it.

I know there are a few of us who follow this pattern occasionally with one of their CW or other watches. I wonder whether you have any thoughts on it.

Does timekeeping improve if you wear a given watch for a prolonged period?

^^^ I’ve just noticed that the photo I took for CWLotD yesterday was showing 31st June. That’s how OCD I am!

I get your point, Steve, but it's hard for me to comment as I rarely wear any watch for more than a couple of days, so it's hard to judge.

The only one that has come close is my C60 Anthropocene GMT (CW logo), which I wore on holiday for 8- 9 days last September. Even then, it wasn't worn 24 / 7 as I wore a different watch in the evening and nothing overnight.

However, timekeeping on the Anthropocene was steady, albeit -15 to -18 sec/day. .

Maybe, one day, I'll get a watch that gets worn more regularly.

Guy

Sent from my Galaxy S23 Ultra using Tapatalk

31 June? I just noticed that yesterday my CWL of the day was also on 31.

I tend to keep two or three running at any particular time, two of which will likely be worn at some point during a 24 hour period. It is usually the case that the watch with the longest power reserve of the three (typically 70 hours) will run with the best precision and accuracy.

I have on a few occasions worn the same watch (as one of three) for a couple of months. IIRC I have tried this with four different watches. The best two performances were a cumulative +0.5s over 72 days and cumulative +2.5s over 116 days.

Neil

@nbg
Not sure I can match those figures, Neil, but in rough and ready terms it’s good to know I can pretty much set and forget when I go away.

I'm not sure that the timekeeping is actually better but our observation of the timekeeping gets better. Yes, operating at the top of the power reserve for long periods should steady out the rate and give the best performance (as opposed to the tail end of the power reserve which usually increases the rate). Wearing on wrist should also steady the temperature more (unless the ambient temperature is drastically changing) which would have some effect as well.

Timekeeping is all about positional averages for the most part. It is hard, unless you have specialized equipment, to simulate the wear experience without, well, wearing it! Nothing averages out positional variance like old fashioned, long term, actual world wear. There will be variations in your activity and the positions that the watch experiences from day to day. So the more days that you wear a single watch consecutively, the more those variations are averaged out.

In my own personal testing I have found that 7 days gives a pretty good picture of how a watch is behaving. 14 days would probably be better. Accuracy testing durations for COSC and METAS are probably good guides to use for duration as those numbers would have been derived by testing and not just observation.

rkovars wrote: ↑Tue Jul 02, 2024 11:53 am Timekeeping is all about positional averages for the most part. It is hard, unless you have specialized equipment, to simulate the wear experience without, well, wearing it! Nothing averages out positional variance like old fashioned, long term, actual world wear. There will be variations in your activity and the positions that the watch experiences from day to day. So the more days that you wear a single watch consecutively, the more those variations are averaged out.

A very good way of putting it, Rich. Watches are meant to be worn, QED. As to temperature variations, well it’s hovering around 20° (68° in your coin) here, but I’m off to Greece in a day or two and it’s mid-30s (90s) there. We shall see. It will be seeing some action in the big blue salty pool!

Amor Vincit Omnia wrote: ↑Tue Jul 02, 2024 12:22 pm

rkovars wrote: ↑Tue Jul 02, 2024 11:53 am Timekeeping is all about positional averages for the most part. It is hard, unless you have specialized equipment, to simulate the wear experience without, well, wearing it! Nothing averages out positional variance like old fashioned, long term, actual world wear. There will be variations in your activity and the positions that the watch experiences from day to day. So the more days that you wear a single watch consecutively, the more those variations are averaged out.

A very good way of putting it, Rich. Watches are meant to be worn, QED. As to temperature variations, well it’s hovering around 20° (68° in your coin) here, but I’m off to Greece in a day or two and it’s mid-30s (90s) there. We shall see. It will be seeing some action in the big blue salty pool!

Have a great trip! The difference in temperature shouldn't make too much of a difference after everything 'acclimates'. Watch movements are largely brass with rhodium and other plating. This makes them vulnerable to variations in temperature. So if you are in a climate where it is 50 in the morning and 90 in the afternoon you should see some variation due to temperature (although very small I think). But if you are in a climate where it doesn't vary wildly the movement should get to a pretty good steady state.

@rkovars

After 3 days in Greece it’s rock solid at +1 s/d.

Steve, you have presented an excellent question. While I own enough watches to rotate, I tend to wear one watch for several days before moving on to the next. Like yourself, I prefer to travel wearing one watch. Simple. The last two years, I have worn my Sealander GMT to Kauai. While not a chronometer or Cosc rated, my Sealander GMT only lost 18 seconds in 9 consecutive days of wear. Well within Cosc tolerance & good enough for me. I agree with the point that has already made, mechanical watches are made to be worn & will perform best when they are. One variable that I hadn’t given a lot of consideration is body temperature & a more consistent climate might help accuracy. I do wear mine while sleeping because if I wake up during the night, I like to easily be able to tell the time at a glance. I really hadn’t thought about Kauai being a tropical island with a narrow temperature range compared to Kansas with its sudden, wide temperature swings being a factor. Regardless of how much difference that makes, my experience with the Sealander GMT is that movement provides a superior performance & is worth the extra cost in addition to the GMT function!

Delmar

I have the same watch and I also noticed how accurate this movement is. Mine is between -1/+1 after a few days of wearing it constantly. Great movement, worth the extra money imo.

I set it to Greek time before leaving Stansted, and back to UK time 1 week and 4 hours later. It had gained six seconds.
Good watch!

After a service, a watchmaker will regulate a watch in various positions for an averaged rate. If you wear the watch and note the actual rate over an extended period of time of normal wear, you could ask your watchmaker to regulate it accordingly.

I think it's a matter of luck if you get a really accurate watch. (Or statistics). I expect movements are designed to achieve accurate timing, and the actual timing falls on a bell curve, based around the standard deviation..

According to Wikipedia, you get 68/95/99.7 % at 1,2 and 3 standard deviations, so say they aim for a standard of 6 seconds, then 68% are +-6 seconds, 95% are +-12secs and most are within +-18secs. A very few might be out of spec. They won't want too many that have to be rejected under warranty.

So we've generally got a pretty good chance of getting within 10spd, I would think.

They pack cornflakes in the same way to ensure packs are slightly overweight and very rarely underweight.

Edit
If you buy a better grade movement, I presume the manufacturing process is different, and the SD they aim for is much less, so they get very few rejections, even at COSC level requirements.

Resurrection to add another idea. I put this watch on (cold start, no winding, power up on the wrist) on Monday, and after 72 hours…


When I took it to Malta in April it gained 22s over 8 days. Still very good. It goes to show that even these very precise/accurate chronometers are subject to slight variations depending on external conditions/positions/state of wind &c.