Welcome to "The Gods Are Bored!" The title of this post is "teacher lingo." It means that you must have some written proof that your students have learned what you set out to teach them.
But I think "results must be measurable" can apply to lots of other things as well.
For years I wondered why Christmas came five days after the winter solstice, and not right on it.
Voila! I'm not the quickest thinker, but I might have figured it out.
After the shortest period of daylight each year, we gain a half minute to a minute of extra daylight per 24-hour cycle. I guess it would take five days or so before the extra daylight would be measurable. It's like our ancient forebears had to be certain that the Sun was returning before they threw a party for it.
Yuletide, explained ... at least to my not-so-nimble mind.
On behalf of the staff of "The Gods Are Bored," and all the Ancient Ones whose praise and worship teams marked this part of the year with feasts, I wish you a peaceful and pleasant holiday. Set some mulled wine aside for the faeries, sing a carol or two, and enjoy the company of your nearest and dearest.
Blessings to all,
Crazy Buzzard Lady