In the data entry screen, if you enter a date before 1753, a message is displayed informing you that the Old Style (Julian) calendar may have been in use. Now a more detailed message is displayed. Although this message is helpful, the change from the Old Style (Julian) to the New Style (Gregorian calendar) happened at various times in different countries, from as early as the late 1500’s to the early 1900’s. Now a more detailed and informative message is displayed with information on when the calendar change occurred in different countries.
Keep in mind that even for dates after 1753 and as late as the early 1900’s the Old Style calendar was observed in some countries. By entering any year prior to 1753, detailed information on dates when the New Style calendar was first used in different countries is displayed.