In 45 BC a standard calendar was adopted by Julius Caesar--each year would have 365 days, and every fourth year have an extra day--the 29th of February. However this calendar was not quite accurate enough to track the true solar year, and it became noticeable that the onset of the seasons was shifting steadily through the year. In 1582 Pope Gregory XIII ruled that a new style calendar should take effect. From then on, century years would only be leap years if they were divisible by 400. Furthermore the current year needed an adjustment to realign the calendar with the seasons. This new calendar, and the correction required, were adopted immediately by Roman Catholic countries, where the day following Thursday 4 October 1582 was Friday 15 October 1582. The British and Americans (among others) did not follow suit until 1752, when Wednesday 2 September was followed by Thursday 14 September. (Russia did not change until 1918, and Greece waited until 1923.) Thus there was a long period of time when history was recorded in two different styles.
Write a program that will read in a date, determine which style it is in, and then convert it to the other style.