A recreation of a traditional seventeenth century Japanese clock.

Daimyo clock is a recreation of a mechanical clock developed in the seventeen century based on western clocks but modified to show traditional Japanese time.
Traditional Japanese time divides the day and night into six equal periods from dawn to dusk and dusk to dawn respectively. Over the course of a year as the daylight and nighttime periods lengthen and shorten, the length of these six day or night periods change. Unlike Western clocks which are regulated by a single pendulum and run at a constant speed day or night, Japanese clocks incorporated two pendulums, and switched between then at dawn and dusk. Adjustment for the changing daylight and nighttime hours was accomplished by adjusting the effective length of the pendulums, normally done every two weeks, or twenty-six times a year. This kept the time shown on the clock reasonably close to the correct time, provided that the clock had been set correctly initially.
This modern implementation is much more accurate and precise than the original clocks. In this implementation, the biweekly adjustments of the mechanical clock are made continuously, thus the day or night period length are always correct. Noon on the clock will, if location services are enabled, occur when the sun is at the zenith, or solar noon. Day start and end correspond to the beginning or end of twilight, and are calculated accounting for the refraction of the Earth's atmosphere.
There are three situations where the clock my not show the local time in the Japanese manner:
1. If location services are off, Daimyo Clock will show the time for Tokyo, Japan. 東京 will be displayed on the clock face in this case.
2. While the application is obtaining an updated location after launch or returning to foreground.
3. Near the North or South poles the sun may either be above the horizon or below it for the entire day (24 hour period). In this case, the Japanese definition of time no longer applies, so the clock face will be shown without a clock hand.

What’s New

Version 1.0.0

This app has been updated by Apple to use the latest Apple signing certificate.

Ratings and Reviews

4.0 out of 5
1 Rating

1 Rating

Oklahoma Hank ,

Interesting, but more would be fun

It would be nice if it translated the Japanese symbols and told you which division and zodiac sign it is showing. As in, third division of the rat, or whatever.

App Privacy

The developer, Douglas Hildum, has not provided details about its privacy practices and handling of data to Apple.

No Details Provided

The developer will be required to provide privacy details when they submit their next app update.


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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