Just in case Yashrus20 hasn’t recovered…
R’ Moshe Sternbuch asks why is it that yidden arrange their calendar based upon a lunar calculation, when most other religions base their’s upon a solar calculation.
The Moon has no light of its own. Any illumination viewed from the moon is basically a ricochet from the sun.
Likewise, Klal Yisroel understand that Olam HaZeh is comparable to Choshech (night i.e. moon), and the light of Olam HaZeh is only from the sun (Olam HaRuchni, the spiritual world).
We can enlighten the darkness of this world only through d’vakus b’hashem in Torah and Mitzvos.
This is the the lesson of the lunar calendar.