Historical CalendarThere is a ten-day difference between the Julian and Gregorian calendars, complicating comparing dates across countries in early modern Europe. This calendar makes it easy to see why Britain had a Friday the 13th in 1588, but Spain did not. The multi-country Historical Calendar permits easy comparison of the Julian and Gregorian calendars for thirteen Western countries between 1000 and 2100. Select a date to discover what that day was called in each country. The site also features a handy explanation of both calendars.