In the 17th century it was calculated that according to the Bible, the Creation of the world has happened exactly 4.000 years before Christ. That was taken as a zero year for the masonic calendar. Today it’s 6007 A.L., or Anno Lucis – The Year of The Light.
Still – different masonic bodies have different time measurements.
Scottish Rite Masons count the time using the Jewish calendar. In order to get the proper year, add 3.760 to the current year. Also, a curiosity is that the year starts in September.
Royal Arch Masons – count the time from the time when the second Temple was started by Zerubbabel. They call it The Year of The Discovery – Anno Inventionis (A.I.). Add 530 to the current year.
Knights Templar's era starts with the formation of their order in 1.118, and it’s called Anno Ordinis (A.O.) - The Year of The Order. According to their calendar, today is year 889.