- There was no year 0, in fact there was no number 0 when the Julian Calendar was created. The year before 1 AD was 1 BC.
- If Christians celebrate Jesus' birth on December the 25th was this is 1 AD or 1 BC? The start of the Julian calendar was March the 25th (nine months before 25th of December) and the time of the vernal or spring equinox at the time. The autumnal equinox was changed to be March 21st a few decades later. This assumed that Jesus came to earth March 25th (nine months before Dec 25th), the first day of 1 AD. March the 25th was also considered the anniversary of Creation. Sept means 7, Oct means 8 and Nona means 9th, and Dec mean 10th and in Roman times they were the Seventh, Eighth, Ninth and Tenth months.
- Julius Caeser named the month he was born, July after himself. He added a day to it to be 31 days from the last month of the year, then February. Caeser was his family name but it later became a title. He was followed Octavian, who named himself Augustus Caeser after his adopted father, and the month he was born in became August. This is why February is so short.
- Pope Gregory XIII - introduced the Gregorian Calendar in 1582 which placed January the 1st as the first day of the year, which was adopted in a few years in Catholic countries. Protestant countries didn't accept it until centuries later. This meant there as a 10 to 11 day time difference between England and French for centuries. When British Empire adopted the calendar, it lost eleven days from September. The day after Wednesday, 2 September 1752 was followed by Thursday, 14 September 1752. Even today, the British tax year starts April the 6th which is based on the March the 25th in the Julian Calendar.
- The USA didn't drop 11 days, instead it adopted the calendar retrospectively. As a result George Washington was born February 11, 1731 but his birthday changed to February 22, 1732 in his lifetime (since the start of the year had also changed)