Audemars Piguet Equation of Time: AP Goes Solar

Audemars Piguet Royal Oak Equation of Time

There are a lot of perpetual calendars on the market, some more interesting than others.  But, Audemars Piguet takes the traditional perpetual calendar a step further with the Equation of Time.  So, I was delighted when I was offered the opportunity to get up close and personal with the Audemars Piguet Royal Oak Equation of Time.

In addition to the usual and customary Perpetual Calendar, the AP Equation of Time is built to a particular latitude and longitude of the location named on a ring around the dial, the only EOT to be set such precise coordinates.  This particular watch is set to New York.  By setting the movement to New York, the registers at the nine o’clock and three o’clock positions indicate the sunrise and sunset times for New York every day.  

To add icing to the horological cake, the thin sweep hand indicates siderial or solar time, since “legal” or “calendar” time can be off as much as sixteen minutes in order to keep days an even twenty-four hours.  Just take the time and add or subtract the minutes indicated by the skinny hand.  And, poof, sidereal time.  Easy.

The Audemars Piguet Royal Oak Equation of Time has one more trick up its sleeve.  The “11h55” refers to the mean solar culmination for New York, that is to say the average time the sun is at its zenith.  Again, by adding or subtracting the minutes indicated by the thin sidereal hand from the mean, you can easily determine when the sun will be at its highest point.

Add in date, day, month, leap year and moonphase indication and you have quite the little astronomical timekeeper.  The AP EOT does all of this with a 41 jewel, 425 part self-winding movement (calibre 2120/2808) that’s only 5 mm thick housed in a 42 mm stainless steel or 18k rose gold case.

AP EOT Movement is only 5 mm Thick

On the wrist, the 42 mm case is a bit large for me, but not excessively so.  It is rather heavy, though.  It’s not uncomfortable, but it’s not comfortable either.  The Audemars Piguet Equation of Time would take a few days to really get used to wearing. 

This movement is undeniably cool.  But, for some reason it gets lost in a Royal Oak case.  The Audemars Piguet Jules Audemars Equation of Time seems a better fit for such a movement.  A simpler case to highlight the watch’s complications.  Either way, the Audemars Piguet Royal Oak Equation of Time is worth a look.


  • Reference: 26603OR.OO.D092CR.01
  • Case Width: 42.00 mm
    Case Thickness:
    10.45 mm
    Water Resistance: 20 m 
  • Functions: Sunrise and sunset times, equation of time, perpetual calendar, astronomical moon, hours, minutes
  • Movement thickness with module: 5.00 mm
  • Total diameter: 12.5 mm
  • Type of balance: With Variable inertia blocks
  • Frequency of balance wheel: 2.75 hz
  • Type of balance-spring stud-holder: Mobile stud
  • Balance-spring type: Flat
  • Direction of automatic winding: Bidirectional
  • Type of oscillating weight: Support and weight segment in 21-carat gold
  • Number of jewels: 41
  • Power reserve: 40 h
  • Number of parts: 425

Author: Nick Glasnovich

Founder & Executive Editor of

Share This Post On

Submit a Comment

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.