In Genesis chapter one when Elohim created the sun and moon, he called the former “the greater light” and the latter “the lesser light” (Gen 1:16). The former rules the day and the lesser rules the night (ibib.). This is prophetic of the role of Yeshua and the saints in the world.
Yeshua the Messiah is the Light of the world (John 1:6–9; 8:12; 9:5) or the Sun of Righteousness (Mal 4:2) or the Greater Light to show man the path of spiritual light in the darkness of this world. The saints are like the moon or the lesser light that reflects the light of the sun or the greater light into the darkness of this world. Yeshua shines his spiritual light onto his disciples who then take that light and evangelize those lost in spiritual darkness with the message of the gospel. This is the great commission!
The biblical feasts are calculated based on the lunations of the moon. The seven biblical holidays speak of YHVH’s plan of salvation to show man the way to Yeshua who is the Greater Spiritual Light as represented by the sun. The feasts are like a tract or sermon by which the saints preach the gospel message of salvation to the world. The saints as the lesser light reflecting the message of salvation through Yeshua the Greater Light into the darkness of this world through their adherence to the biblical feasts. This is one reason why the moon—the lesser light—is so pivotal to YHVH’s calendar and feasts.
The traditional calendar currently used by the non-believing, rabbinic Jews is off; it’s not in accordance with the moon though the Jews erroneously purport it to be. At the same time, they’re not bringing the gospel message of Yeshua to the world—only the doctrines of men and men’s traditions. Their whole message is askew and fails to reflect the Greater Light of Yeshua.
Similarly, the mainstream church tries to preach the gospel, but without understanding the moon, feasts and biblical calendar their message of the gospel is only a partial one and is also off spiritually.
A time may come in the future when the calendar and feasts will go strictly off the sun and not the moon. This may occur when there is a new heaven and a new earth when Yeshua is ruling on this earth and he will be the only Light of the world. That time isn’t yet, though, for it’s still the saints’ job as the lesser light to be like the moon to reflect the truth of Yeshua, the Greater Light, to this world through a lunar-based calendar upon which the biblical feasts are based.