Occasionally, there is ambiguity regarding the year designation A.L. on a Masonic document. I have found the following references in A Comprehensive Dictionary of Freemasonry by Ernest Beha, New York, New York: Citadel Press, 1963.
Anno Domini (A.D.)
This is the Latin for “In the Year of Our Lord”. It is also called the Vulgar Era, referring to its common or general use, a term which perhaps will fall into disuse eventually. The Masonic year, or “The Year of Light” is 4,000 years ahead of Anno Domini. (See Anno Lucis.)
Anno Lucis (A.L.)
This is Latin for “In the Year of Light”. The term is frequently used in Masonic procedure, and expresses a year that is 4,000 beyond Anno Domini (“The year of Our Lord”). There is a reason for this, of course. The date of the creation of the world is generally assumed to be 4,000 years before the birth of Our Lord, and the creation of the world saw the beginning of Light. (“Let there be Light. And there was Light.”)
Dr. James Anderson, in his 1723 “Constitutions”, refers to the 4,000 year-advanced “Anno Lucis” as “The Year of Masonry” and the idea was adopted. That is why a Mason’s Grand Lodge registration certificate has two dates recorded thereon, the Year of Light (or the Year of Masonry) and the accepted everyday calendar year (or the “Year of Our Lord”).
Therefore, if a person were made a Mason in 1955, this year (and the precise date) would appear on it, as well as the Anno Lucis date, which would be 5955 and in Iowa the date on his 50 year certificate if he lost no time would be 6005. (See below)
Anno Mundi (A.M.)
This is the Latin for “In the year of the World”. Used in some Degrees practiced abroad. Roughly calculated it is 3,760 years before Anno Domini. (See Anno Lucis.)
Anno Ordinis (A.O.)
This is the Latin for “In the year of the Order”, The term is used in Knight Templary and is found by subtracting 1118 from the everyday calendar.