Lunar calendar or crescent moons and others employing detailed calculations. Since each lunation is approximately days (29 days, 12 hours, 44 minutes, 3 seconds, or days), it is common for the months of a lunar calendar to alternate between 29 and 30 days. Since the period of twelve such lunations, a lunar year, is only 354 days, 8 hours, 48 minutes, 34 seconds ( days), purely lunar calendars lose around 11 days per year relative to the Gregorian calendar. In purely lunar calendars like the Islamic calendar, the lack of intercalation causes the lunar months to cycle through all the seasons of
Apollo 15 operations on the Lunar surface triangles are panorama stations. Apollo 15 operations on the Lunar surface Apollo 15 lunar surface operations were conducted from July 30 to August 2, 1971, by Apollo 15 Commander David Scott and lunar module Pilot James Irwin, who used the first lunar rover to make three exploratory trips away from their landing site at the base of the Apennine Mountains, near Hadley Rille. They collected a total of of lunar surface material during 18½ hours outside their lunar module, "Falcon". At 104 hours, 30 minutes and 12 seconds GET the descent engine of "Falcon" ignited. Burning at about 10% for