Solar eclipses occur two to five times a year, though it is rare for five to occur in a year. The last time five occurred in a single year was in 1935, and the next time five are expected in a year is no earlier than 2206. Total eclipses (with the Sun fully covered) are even rarer—the average number of total solar eclipses in a century is 66 for Earth as a whole. This rarity is due to the specific alignment required between the Sun, Moon, and Earth for a total solar eclipse to occur. By contrast most calendar years see two lunar eclipses; in some years one or three or none occur.