Girard-Perregaux 99240D52A801-CK8A, User Manual

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77
English
E
QUATIONžOFžTIME
)NTRODUCTION
The Earth’s orbit around the sun is not perfectly circular. As with most of the celestial bodies in
OURžSOLARžSYSTEMžITSžTRAJECTORYžISžELLIPTICALž)NžADDITIONžTHEž%ARTHmSžAXISžISžTILTEDžINžRELATIONžTOžTHEž
ORBITmSžPLANEž!žCONSEQUENCEžOFžTHISžIRREGULARžTRAJECTORYžISžTHATžTHEžLENGTHžOFžTHEžSOLARžDAYžqžTHEž
interval between the times at which the sun twice passes the meridian at a given location – varies
according to the season. The 24-hour day used for civil time is calculated using the average
duration of the solar day.
2EADING
The equation of time function indicates the difference between the mean time and the solar time.
This difference is indicated by a little hand which moves along a graduated arc. It can extend
to between approxi14 and –16 minutes for certain dates at the start of February and
November respectively.
3ETTING
The equation of time indicator is synchronized with the calendar readings, and therefore does
NOTžREQUIREžADJUSTMENT
Beginning February
Beginning November