Free Printable January 2020 Calendar - Wiki-Calendar. ComHow Many Days Were In The Julian Calendar? Interesting facts about the month April you didn't know and its HISTORYWhy does February have 28 days? | #aumsumIanuarius, fully Mensis Ianuarius, was the first month of the ancient Roman calendar, from which the Julian and Gregorian month of January derived. It was followed by Februarius ("February"). In the calendars of the Roman Republic, Ianuarius had 29 days. Two days were added when the calendar was reformed under Julius Caesar in 45 BCE.