Their calendar, which they believed came from the instruction of the Lord, begins the year with the Spring Equinox, March 20th on our Gregorian Calendar. This, of course, agrees with the command of the Lord that the month in which Passover occurs is first month of the year (Exodus 12:2). The Essene Calendar has 364 days, which is exactly 52 weeks. This means that the calendar never changes. Every year begins on Thursday, and the Holy Days always occur on the same day of the week. Passover, for example, always begins Thursday evening an sunset.

I have created a parallel Essene/Gregorian calendar. There are two versions; the Normal Year and the Leap Year. Because the Essene Calendar always begins on the same day, my parallel calendars will work for any year. You can research when any historic event occurred on this calendar. The only caveat is whether or not the Essene Calendar is indeed the calendar prescribed by the Lord. I suspect that it is.