Gregorian Calendar

The calendar now used internationally, devised by Pope Gregory in the 1580s to replace the Julian calendar, which by then had accumulated a ten-day discrepancy with the solar year. Most, but not all, countries accepted the Pope’s calendar by the 1700s (Great Britain, 1752). Russia did not change until 1918 and Turkey in 1928. Astrologers working with older dates should determine whether they are based on the Julian calendar, designated Old Style or OS, or on the Gregorian calendar, designated New Style or NS.