I’m wondering what the correct terms is for historical anchors or chronological rosetta stones - that is, unmistakable events in the past such as eclipses that have been used by historians to sync up disparate calendar systems. Also wondering if there is a good resource listing some of these events and/or some sort of official reference or program for converting between calendar systems and time formats that includes tricky things like time zones, daylights savings, and the missing year zero.