Dear All, Apologies if this question isn’t really in the right place. I wanted to check I’ve understood some data correctly. The link below shows lunar cycles all the way back to 2000 BC: http://astropixels.com/ephemeris/phasescat/phasescat.html. Suppose I click on a table and get a date of 1st June 750 BC for some event or other. How could I work out the number of days between that date and, say, 1st June 751 AD? Is it simply 1500 * 365.25? Or do I need to use the length of a tropical year in such calculations. James.