Calendar Help Please?

Julian dates are a count of days and fractions of days that have elapsed since noon Universal Time on January 1, 4713 BCE, the first day on the Julian calendar. (Fast Fact: Almost 2.45 million days have transpired since this date. I just checked. ;-)) They are used because the calendar dates we are accustomed to seeing (mm/dd/yy) have varies depending upon the different calendar systems that may have been used throughout history.

If the calendar you're looking at has normal calendar as well as Julian dates, I'm sure you'll be fine: I assume it would just be a little interesting side note in each square. In the event that you get it and it's not, the US Naval Observatory website linked below has a handy little converter (and an more in depth description).

Hope that helps! :-)