[William Cloud Hicklin]

A couple of things to note about Durin's Day

1) The definition given is the "first day of the last moon of autumn."

2) As noted above, "first day" must refer to the first visible crescent, not the astronomical New Moon which is invisible

3) Here's where it gets odd: the text has, the day prior, "Tomorrow begins the last week of autumn." But don't the Dwarves use a lunar calendar? At least their New Year is defined in lunar terms: the first day of the last moon of Autumn. Do they define their seasons on a solar basis? It seems the only way to make it work, if the season is held to begin just a week after the new moon.

4) However, if the Dwarves are using a mixed solar/lunar calendar it might at least help explain how "it passes our skill in these days" to forecast Durin's Day occurring.

5) Nonetheless, surely one of the brighter bulbs among the 13 would understand that even though one can't forecast that DD will occur in any given year, one certainly can predict on which day of the year it must happen if it happens at all: to wit, the first day of the last autumn moon.

So, yes, stupid Dwarves: one would think they would have been lurking eagerly around the stone on that day, key in hand, from late afternoon onward.