Dating range calculation
The term "holiday" can be interpreted differently, depending on region. Generally, holidays are meant to commemorate some event, person, or group of cultural or religious significance.
Although certain holidays, such as Christmas and New Year's Day, are widely celebrated worldwide, most countries have their own set of holidays that are specific to the country, and even the same holidays may be observed differently within countries: some may receive full suspension of typical daily activities, while others may only get partial days off.
The ancient Roman calendar was believed to be an observational lunar calendar, based on the cycles of the moon's phases.
The Romans were then believed to have adopted a 10-month calendar with 304 days, leaving the remaining 50 or so days as an unorganized winter.
Under the Gregorian calendar, century years not divisible by 400 would not be leap years.
These changes reduced the error from 1 day in 128 years, to 1 day in 3,030 years with respect to the current value of the mean solar year.
By 1582, this resulted in a difference of 10 days from what was expected.Are you wondering when your pregnant mare will foal? The average gestation length in the mare ranges from 320 to 362 days; most mares will foal within 330-345 days of successful breeding.However, mares have successfully foaled with gestation lengths outside this range.Pope Gregory XIII addressed this by essentially skipping 10 days in the date, making the day after October 4, 1582, October 15.An adjustment was also made to the algorithm of the Julian calendar that changed which century years would be considered leap years.