The ancient Egyptians did not have a single, consecutive era like our modern use of years before and after Christ. Instead, they dated their documents and events according to the regnal year of the reigning king. Egyptian records of astronomical observations were also often dated to a certain regnal year. Attempts have been made to calculate when these astronomical events took place and determine the absolute date in terms of our calendar. However, there are many imponderables which means that often more than one absolute date BC is possible for an ancient Egyptian date.