I live by the modern Gregorian calender. The Gregorian calendar is the most widely used calendar in the world. A modification of the Julian calendar. "Although the Julian calendar remained in use into the 20th century in some countries and is still used by many national Orthodox churches, it has generally been replaced by the modern Gregorian calendar."-wikipedia-

The Gregorian solar calendar is an arithmetical calendar. It counts days as the basic unit of time, grouping them into years of 365 or 366 days. The solar calendar repeats completely every 146,097 days, which fill 400 years, and which also happens to be 20871 seven-day weeks. Of these 400 years, 303 (the "common years") have 365 days, and 97 - the leap years - have 366 days. This gives an average year length of exactly 365.2425 days - or 365 days, 5 hours, 49 minutes and 12 seconds.

-Wikipedia-