That is why February became 30 days that yearFor many years, most Western countries used the Julian calendar, named after Julius Caesar. According to that calendar, the number of days in the first three years of every four years is 365 and in the fourth year the number becomes 366. In 1582, Pope Gregory VIII introduced the Gregorian calendar. He did this primarily to make Easter more closely aligned with the seasons. But Sweden did not make this change immediately. In the late 17th century they decided to eliminate the leap years from 1700 to 1740 to reduce the difference between the Swedish and Gregorian calendars. But later on, Sweden decided to return to the Julian calendar. Then two leap days were kept in 1712 to avoid confusion of dates. These days were 29th and 30th of February.The Gregorian calendar was fully used in the country in 1753.