Most Christian countries celebrated the day they believed the angel Gabriel visited the Virgin Mary and told her that she would be the mother of Jesus Christ. Since they celebrated December 25 of each year as the birth of Christ, they designated March 25 (nine months before) as the day of Gabriel's visit. They called it the Day of Annunciation. In England the traditional name for the day was Lady Day.
In England, Lady Day was also New Years Day from 1155 until 1752 so each year began on March 25. When the Gregorian Calendar was adopted in 1752 the new year began on January 1.
Months of the year from 1155 to 1752
March 25-31
April
May
June
July
August
September
October
November
December
January
February
March 1-24
Months of the year after 1751
January
February
March
April
May
June
July
August
September
October
November
December
Since in the Lady Day calendar the new year begins with March 25, it is easy to become confused about which year the time frame from January 1 through March 24 belongs to. This causes problems for people doing genealogical research.
An example of the problem is the christening and burial of two daughters of William and Mary Wight(e) both named Ruth in the Great Gonerby parish. The first daughter was christened 18 July 1742 and buried 17 September 1746. The second daughter was christened 26 February 1746 and buried 25 June 1747.
In this example it appears that William and Mary had two daughters named Ruth living at the same time in 1746. The second Ruth was christened in February and the first was buried in September of 1746. It was a common practice for parents to give a child the same name as an older sibling that had died; but in this example it looks as if both girls were alive from February to September.
However the left column of the chart shows that in the Lady Day calendar, February came after September, so the burial of the first Ruth in September 1746 was before the christening of the second Ruth in February 1746.
