<p><span class="h-card" translate="no"><a href="https://mastodon.social/@whitequark" class="u-url mention">@<span>whitequark</span></a></span> This: <a href="https://github.com/EdReingold/calendar-code2/blob/9afc1f3/calendar.l#L3985-L4035" target="_blank" rel="nofollow noopener noreferrer" translate="no"><span class="invisible">https://</span><span class="ellipsis">github.com/EdReingold/calendar</span><span class="invisible">-code2/blob/9afc1f3/calendar.l#L3985-L4035</span></a>.<br />Many calendar implementers just use the implementation from _Calendrical Calculations_ by Reingold and Dershowitz, e.g., ICU4X: <a href="https://github.com/unicode-org/icu4x/blob/9cb01e434ad6af92e77c8046affb1fad2eb54deb/utils/calendrical_calculations/src/astronomy.rs#L1612" target="_blank" rel="nofollow noopener noreferrer" translate="no"><span class="invisible">https://</span><span class="ellipsis">github.com/unicode-org/icu4x/b</span><span class="invisible">lob/9cb01e434ad6af92e77c8046affb1fad2eb54deb/utils/calendrical_calculations/src/astronomy.rs#L1612</span></a>.</p><p>Interestingly I cannot find the same constants in ICU4C and ICU4J so they may be doing something else.</p><p>Re <span class="h-card" translate="no"><a href="https://chaos.social/@gsuberland" class="u-url mention">@<span>gsuberland</span></a></span>’s comment, given the dates, I am guessing it is bosed on VSOP82 or older, rather than VSOP87 or newer.</p>