The Julian Calendar, which the English continued to use from 1582–1752, started the new year on March 25. So December was the tenth month.
Parliament declared that the day after September 2, 1752 was to be September 14, 1752. The change to the Gregorian Calendar, happened in several steps:
• December 31, 1750 was followed by January 1, 1750.
• March 24, 1750 was followed by March 25, 1751.
• December 31, 1751 was followed by January 1, 1752
• September 2, 1752 was followed by September 14, 1752.
By September 14, 1752 the English (including the Colonies) had switched to the Gregorian Calendar and were using the same dates as the rest of Europe. The year 1752 was 72 days shorter.
Is it all clear now?
Any document dated January 1st through March 24th, before 1752, is one year off.
