Use this horology calculation to interpret a stated watch, clock, timing-machine, water-resistance, alarm, or historical respiratory-timing quantity under its defined convention.

Display Cycle Days (day)

Required number input.

True Synodic Days (day)

Required number input.

Signed lunar-phase error in equivalent lunar days per Julian year from the displayed and true synodic cycle lengths. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Phase Error Days Per Year (day/year)

The resulting phase error days per year returned as a number.

• Mechanical-watch amplitude and beat measurements depend on lift angle, position, state of wind, movement condition, instrument setup, and elapsed sampling. ATM markings are test-pressure classifications rather than literal safe diving depths.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Confirm movement specifications and measure in multiple positions and power states; follow the manufacturer's water-resistance guidance and obtain pressure testing after case service.

• Moonphase Correction Days

  Years until an absolute one-day lunar-phase display error from a nonzero drift measured in lunar days per year.

• Daily Rate To Annual Drift

  Signed clock drift over a supplied year length in days from seconds gained or lost per day.

• Synodic Cycle Display

  Moon-phase display cycle in days from gear tooth count and advances per calendar day.