Lunar month circular, the speed of Earth's progression around the Sun varies during the year. Thus, the angular rate is faster nearer periapsis and slower near apoapsis. The same is so for the Moon's orbit around the Earth. Because of these variations in angular rate, the actual time between lunations may vary from about 29.18 to about 29.93 days. The long-term average duration is days (29 d 12 h 44 min 2.8016 s). The synodic month is used to calculate eclipse cycles. It is customary to specify positions of celestial bodies with respect to the vernal equinox. Because of Earth's precession of
1920 Isle of Man TT 44 minutes and 6 seconds, an average speed of 51.36 mph. A mechanical retirement for Eric Williams allowed Cyril Williams also riding an AJS to build up an impressive lead of 20 minutes. However, Cyril Williams hit transmission problems at Creg-ny-Baa and free-wheeled and pushed it for the last five miles to win by a margin of 9 minutes and 50 seconds from J.A.Watson-Bourne, riding for Blackburne motorcycles in 4 hours, 37 minutes and 57 seconds, at an average race speed of 40.74 mph. The Lightweight class within Junior race was won by R.O Clarke riding a Levis and he