The Julian Calendar was a calendar designed by the Alexandrian astronomer Sosigenes in 46 BC and enforced throughout the Roman Empire by Julius Caesar in 45 BC. It remained in use throughout the Western world until 1582, when inaccuracies in the Julian calendar were found to have created a lag of ten full days in the Julian calendar; for instance, the vernal equinox was marked ten days after the day which had twelve hours of sunlight and twelve hours of darkness. A revised calendar correcting this problem, the Gregorian Calendar, was proposed to and decreed by Pope Gregory XIII. The Julian Calendar was abandoned in Catholic countries but remained in use in Protestant countries for centuries. Many Eastern Orthodox countries use either the Julian calendar, or a variation.
Julian Calendar in Ruled BritanniaEdit
When Spain invaded and conquered England in 1588 and made Catholicism the official state religion of that kingdom, they imposed the Gregorian Calendar by removing 10 days from the month of June 1589, and suppressed the Julian Calendar.
In 1598, the Paschal Moon fell on the same day as the vernal equinox according to the Gregorian Calendar: a day which the Julian Calendar insisted was still winter, and thus not the Paschal Moon at all. Thus, Protestants and Catholics marked Easter on different days. In England, this forced Protestants who were concealing their identities for fear of Catholic persecutions either to violate the Catholic Lent or their own or to observe both.