Complication · Calendar & astronomy
Sunrise/Sunset Indication
Partially verifiedA display showing the times of sunrise and sunset for a given date and location, usually via two hands or discs read against a 24-hour scale, or a shaded day/night sector whose boundary shifts through the year.
Definition
A display showing the times of sunrise and sunset for a given date and location, usually via two hands or discs read against a 24-hour scale, or a shaded day/night sector whose boundary shifts through the year.
Historical origin
An extension of the astronomical clock and watch tradition, appearing in complicated pocket watches from at least the nineteenth century and continuing in modern high-complication wristwatches; because sunrise and sunset times vary with latitude, such displays are inherently calibrated to a specific location rather than being universally accurate.
How it works
A cam or disc, cut or printed with a profile encoding the changing length of daylight through the year for a specific latitude, is geared to complete one revolution per year and drives a follower that positions the sunrise and sunset hands or a shaded sector accordingly.
Because the cam's profile is calculated for one latitude, the same watch will show increasingly inaccurate sunrise/sunset times as it is used further from the location it was calibrated for, which manufacturers of such complications generally state explicitly.
Some versions combine the sunrise/sunset function with a day/night sector display on the same 24-hour ring, so the shifting boundary between the shaded and unshaded portions of the ring visually represents the changing length of day and night through the year.
Pocket watch context
Found in elaborate nineteenth- and early twentieth-century astronomical pocket watches, often as one of several combined celestial indications on a single dial.
Wristwatch context
A niche but recognised complication in modern high-complication wristwatches, frequently marketed with an explicit statement of the latitude or city the mechanism is calibrated for.
Identification
- Two hands or a shaded sector on a 24-hour scale indicating sunrise and sunset, shifting position gradually through the year
- Documentation or a dial inscription specifying the calibrated location or latitude is a normal and expected feature
Servicing notes
The annual cam profile is calibre- and latitude-specific; servicing and any recalibration to a different location should go to a watchmaker experienced with the particular mechanism.
General guidance only. Complicated mechanisms should be assessed and serviced by a qualified watchmaker or clockmaker specialist, not adjusted at home.
Diagram
Sources & references
- General secondary literature on astronomical complication watches.
- Specific historic and manufacturer claims were not independently verified here.
Where sources disagree, the disagreement is stated rather than resolved silently.