The Julian calendar uses the same month and year as the Gregorian calendar, the calendar most commonly used worldwide. Because the Julian calendar uses a seven-day week, to determine what day of the week it is, the number should be divided by seven.
The Julian calendar assumes a leap day every four years, meaning that each year on a Julian calendar is 365.25 days. The common Gregorian calendar assumes a leap day every four years with the exception of century years, which creates a disparity between the two. The Julian calendar is predominately used by astrologists and was the primary calendar used worldwide before the Gregorian calendar came to prominence in 1582.