Why are most Buddhist dates set based on the Lunar Calendar?
There was a time, before the Romans formulated the Julian calendar (which we use) that Rome too used a Lunar Calendar. In fact, our word “Month” derives from the word Moon (lunar), and no longer directly relates to a true Month; from full moon to full moon. (more than 12 months a year, less than 13) But, we still call it a Month in our (more accurate) solar calendar. Many cultures still use the older, lunar calendar.