Masonic Trivia (10/26/2016).

In some lodges, the date is written "A.L." for "Anno Lucis" (or "In the year of Light") which is 4,000 years plus the current year. For instance, the year 2016 would be written 6016 A.L.

This is because the practice follows the ancient belief that the world was created when God said "Let there be light" ... four thousand years before the birth of Christ.