Anno Universorum (meaning "in the Year of the Universe", abbreviated as AU or A.U.) is a rarely-used year-numbering system based on the birth of the universe, dating back to 13,800,000,000 BC. The system adds exactly 13.8 billion years to the Anno Domini/Before Christ year number and appends the AU abbreviation, e.g. 2013 becomes AU 13,800,002,013. Like Anno Domini, Anno Universorum should properly precede the date rather than follow it, but this is not always followed. The Anno Universorum calendar says that it will be 14,800 million years from the birth of the universe in AU 14,800,000,000, or 1,000,000,000 AD.
The system was devised in 2002 (AU 13,800,002,002) for others to understand when the universe was born and how many years it is later. The devisor, whose name is unknown, stated that, "Anno Universorum is based on the birth of our universe, which we date back to 13,800,000,000 BC." His system was devised for the purpose of replacing the Anno Domini/Before Christ eras that were used prior.