Author here. That&#x27;s an interesting claim -- that the solstices and equinoxes used to fall on the first days of the month. (At least, I think that&#x27;s what you&#x27;re implying.) But I&#x27;m not sure that checks out: The Julian and Gregorian calendar diverge by 3 days every 400 hundred years. When the Gregorian calendar was adopted at various times in various countries, it skipped forward between 10 and 13 days (<a href="http:&#x2F;&#x2F;www.timeanddate.com&#x2F;calendar&#x2F;julian-gregorian-switch.html" rel="nofollow">http:&#x2F;&#x2F;www.timeanddate.com&#x2F;calendar&#x2F;julian-gregorian-switch....</a>). That&#x27;s not enough days to explain why the equinoxes and solstices fall 20 or 21 days after the first of the month. Do you have a source for this?<p>Moreover, I argue that if you want to use astronomical seasons, it doesn&#x27;t make much sense to begin them on the solstices and equinoxes -- they should begin near the &quot;cross-quarter&quot; days halfway in between (around the 7th of March, May, August, and November). And that is indeed how the seasons used to be defined in many cultures, such that Midsummer and Yule, the midwinter holiday, each came near the solstice.