<P> A leap day is observed because a complete revolution around the Sun takes approximately 6 hours longer than 365 days ( 8,760 hours ) . A leap day compensates for this lag , realigning the calendar with the Earth 's position in the Solar System ; otherwise , seasons would occur earlier than intended in the calendar year . The Julian calendar used in Christendom until the 16th century added a leap day every four years ; but this rule adds too many days ( roughly 3 every 400 years ) , making the equinoxes and solstices shift gradually to earlier dates . By the 16th century the vernal equinox had drifted to March 11 , and the Gregorian calendar was introduced both to shift it back by omitting several days , and to reduce the number of leap years via the `` century rule '' to keep the equinoxes more or less fixed and the date of Easter consistently close to the vernal equinox . </P>
<P> A leap day is observed because a complete revolution around the Sun takes approximately 6 hours longer than 365 days ( 8,760 hours ) . A leap day compensates for this lag , realigning the calendar with the Earth 's position in the Solar System ; otherwise , seasons would occur earlier than intended in the calendar year . The Julian calendar used in Christendom until the 16th century added a leap day every four years ; but this rule adds too many days ( roughly 3 every 400 years ) , making the equinoxes and solstices shift gradually to earlier dates . By the 16th century the vernal equinox had drifted to March 11 , and the Gregorian calendar was introduced both to shift it back by omitting several days , and to reduce the number of leap years via the `` century rule '' to keep the equinoxes more or less fixed and the date of Easter consistently close to the vernal equinox . </P>
why there are 29 days in february in a leap year
why there are 29 days in february in a leap year
because a complete revolution around the Sun takes approximately 6 hours longer than 365 days ( 8,760 hours )
because a complete revolution around the Sun takes approximately 6 hours longer than 365 days ( 8,760 hours )