why there are 29 days in february in a leap year
February 29 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.[1][2]
Hundreds and thousands Hundreds and thousands used incorrectly instead of hundreds of thousands to mean "an indefinite but emphatically large number".
Day In common usage, it is either an interval equal to 24 hours[4] or daytime, the consecutive period of time during which the Sun is above the horizon. The word day may also refer to a day of the week or to a calendar date, as in answer to the question, "On which day?" The life patterns (circadian rhythms) of humans and many other species are related to Earth's solar day and the day-night cycle.
1 + 2 + 3 + 4 + ⋯ which increases without bound as n goes to infinity. Because the sequence of partial sums fails to converge to a finite limit, the series does not have a sum.
Julian calendar Although the new calendar was much simpler than the pre-Julian calendar, the pontifices initially added a leap day every three years, instead of every four. There are accounts of this in Solinus,[40] Pliny,[41] Ammianus,[42] Suetonius,[43] and Censorinus.[44]
Week A continuous seven-day cycle that runs throughout history paying no attention whatsoever to the phases of the moon was probably first practiced in Judaism, dated to the 6th century BC at the latest.[8][9]