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
1928 Isle of Man TT held in heavy rain and mist. The bad race conditions produced many retirements and a slow average speed. The eventual winner of the 1928 Senior TT Race was Charlie Dodson, riding a Sunbeam motorcycle, in 4 hours, 11 minutes and 40 seconds, at an average speed of . 1928 Isle of Man TT In the 1928 Isle of Man Tourist Trophy the newly developed 'positive-stop' foot gear-change by Velocette gave Alec Bennett his fifth TT Race win in the 1928 Junior, in the time of 3 hours, 50 minutes and 52 seconds, at an average speed of , and setting