The calendar in the later Tudor period was different from the rest of Catholic Europe due to a change in the calendar ordered by Pope Gregory XIII. The protestant countries did not agree to this and they did not change their calendar for over 100 years and many Catholic counties did not accept the change for months or years. This leads to a confusion of 10 days depending on who was recording the date - a protestant or a catholic.

REASON: The length of a day is the time that the earth turned once on its axis. The length of a year (the tropical year) is the time it takes the Earth to go round the Sun once. Unfortunately for precise calculations the tropical year (in 1994-98) was 365.242190 days long which gained a quarter day each year on the calendar year (secular year). To allow the calendar year to approximately catch on these lost quarter days the "Julian" calendar allowed an extra day every fourth year (leap year). However this over compensated by approximately 1 day in 400 years.

This error of ten days had accumulated over the thirteen centuries since the adoption of the Julian Calendar by the Council of Nicaea in 325. This was considered intolerable by the scholars of that time because of the confusion in the calculation of the date of Easter. They persuaded Pope Gregory XIII to make the change and he decreed that the day after October 4, 1582 would be October 15, 1582. The switchover was bitterly opposed by much of the populace, who feared that either they had lost 10 days of their life or it was attempt by landlords to cheat then out of a week and a half's rent!

The calendar year in the Tudor period (and earlier) in England started on the Annunciation of the Virgin Mary, 25th March, i.e. nine months before the nativity of Jesus on 25th December. Nowadays we use 1st Jan (the feast of the Circumcision of Jesus) as the start of the year. This is why you will find some dates written 1462/3 because the dates between 1st Jan and the 24th March would be in 1462 by the Tudor calendar but in 1463 by our current calendar. Writing 1462/3 allows for this difference.