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
America-class steamship "Europa" was also chartered as a troopship during the Crimean War and continued in Cunard service until 1867, when she was sold and converted to a sailing ship. Won the eastbound record in 1849 with a Halifax–Liverpool voyage of 8 days 12 hours 44 minutes, an average of . During the Crimean War, she remained on the Halifax route and was sold for conversion to a sailing ship in 1866. Took the Blue Riband in May 1850 with a Liverpool–Halifax run of 8 days 14 hours 50 minutes, an average of . "Asia" also remained on the Halifax route during