What signs or seasons role does the moon play?
Ex 12:2 This month (HODESH) shall be for you the beginning of months.
The answer is that the Hebrew word for month (Hodesh) itself indicates a connection to the moon. We can see this connection in a number of instances in which Hodesh (month) is used interchangeably with the word "Yerah", the common Biblical Hebrew word for moon, which by extension also means "month". For example:
"...in the month (Yerah) of Bul,
which is the Eighth month (Hodesh)..." (1 Kings 6:38)
"...in the month (Yerah) of Ethanim... which is the Seventh month (Hodesh)..." (1 Kings 8:2)
Another proof that Hodesh is related to the moon (Yerah) is the phrase "A Hodesh (month) of days" (Gen 29:14; Nu 11:20-21) [meaning a period of 29 or 30 days] which is equivalent to the phrase "A Yerah (month/ moon) of days" (Dt 21:13; 2 Ki 15:13). Clearly then Hodesh is related to "Yerah", which itself literally means "moon".
Ps 104:19 He created the moon for Mo'adim [appointed times]
So when the Psalmist tells us that God created the moon for Mo'adim [appointed times] he means that the moon was created to determine the time of the Mo'adim of Yehovah, that is, the Biblical Holidays.
The primary meaning of Hodesh (month) is actually "New Moon" or "New Moon Day" and it is only by extension that it came to mean "month", that is, the period between one New Moon and the next. This primary meaning is preserved in a number of passages such as 1Sam 20:5 in which Jonathan says to David "Tomorrow is the New Moon (Hodesh)". Clearly, in this verse Hodesh is used to refer to the specific day on which the month begins and not the entire month. Another passage which uses Hodesh in its primary sense is Ez 46:1 which talks about "The Day (Yom) of the New Moon (Ha-Hodesh)". Clearly in this verse Hodesh (New Moon) is a specific event and the beginning of the month is the day on which this event (New Moon) occurs.
"Hodesh" (New Moon), is derived from the root H.D.SH.
meaning "new" or "to make new/ renew". The Crescent New Moon is called Hodesh because it is the first time the moon is seen anew after being concealed for several days at the end of the lunar cycle.
In ancient societies people worked from dawn to dusk and they would have noticed the Old Moon getting smaller and smaller in the morning sky. When the morning moon had disappeared the ancient Israelites would have anxiously awaited its reappearance 1.5-3.5 days later in the evening sky. Having disappeared for several days and then appearing anew in the early evening sky they would have called it the "New Moon" or "Hodesh" (from Hadash meaning "New").
Ps 81:3 [Heb. 81:4] "Blow on a horn for the Hodesh (New Moon)
On the Keseh (Full Moon) for the Day of our Hag (Feast)."
In the Bible, Feast (Hag) is a technical term which always refers to the three annual pilgrimage-feasts (Matzot, Shavuot, Sukkot; see Ex 23; Ex 34). New Moon Day (Hodesh) is never classified as a "Pilgrimage-Feast" so Keseh/ Hag can not possibly be synonymous with New Moon Day (Hodesh). It has further been suggested that Keseh refers to the Biblical holiday of Yom Teruah (Day of Shouting), which always falls out on New Moon Day. However, the Bible describes Yom Teruah as a Moed (appointed time) and never as a Hag (Pilgrimage-Feast) so Keseh/ Hag can not refer to Yom Teruah either.
Keseh is related to the Aramaic word "Kista" and the Assyrian word "Kuseu" which mean "full moon" This fits in perfectly with the description of Keseh as the day of the Hag since two of the three Pilgrimage-Feasts (Hag HaMatzot and Hag HaSukkot) are on the 15th of the month, which is about the time of the Full Moon!
Ex 12:2 This month (HODESH) shall be for you the beginning of months.
The answer is that the Hebrew word for month (Hodesh) itself indicates a connection to the moon. We can see this connection in a number of instances in which Hodesh (month) is used interchangeably with the word "Yerah", the common Biblical Hebrew word for moon, which by extension also means "month". For example:
"...in the month (Yerah) of Bul,
which is the Eighth month (Hodesh)..." (1 Kings 6:38)
"...in the month (Yerah) of Ethanim... which is the Seventh month (Hodesh)..." (1 Kings 8:2)
Another proof that Hodesh is related to the moon (Yerah) is the phrase "A Hodesh (month) of days" (Gen 29:14; Nu 11:20-21) [meaning a period of 29 or 30 days] which is equivalent to the phrase "A Yerah (month/ moon) of days" (Dt 21:13; 2 Ki 15:13). Clearly then Hodesh is related to "Yerah", which itself literally means "moon".
Ps 104:19 He created the moon for Mo'adim [appointed times]
So when the Psalmist tells us that God created the moon for Mo'adim [appointed times] he means that the moon was created to determine the time of the Mo'adim of Yehovah, that is, the Biblical Holidays.
The primary meaning of Hodesh (month) is actually "New Moon" or "New Moon Day" and it is only by extension that it came to mean "month", that is, the period between one New Moon and the next. This primary meaning is preserved in a number of passages such as 1Sam 20:5 in which Jonathan says to David "Tomorrow is the New Moon (Hodesh)". Clearly, in this verse Hodesh is used to refer to the specific day on which the month begins and not the entire month. Another passage which uses Hodesh in its primary sense is Ez 46:1 which talks about "The Day (Yom) of the New Moon (Ha-Hodesh)". Clearly in this verse Hodesh (New Moon) is a specific event and the beginning of the month is the day on which this event (New Moon) occurs.
"Hodesh" (New Moon), is derived from the root H.D.SH.

In ancient societies people worked from dawn to dusk and they would have noticed the Old Moon getting smaller and smaller in the morning sky. When the morning moon had disappeared the ancient Israelites would have anxiously awaited its reappearance 1.5-3.5 days later in the evening sky. Having disappeared for several days and then appearing anew in the early evening sky they would have called it the "New Moon" or "Hodesh" (from Hadash meaning "New").
Ps 81:3 [Heb. 81:4] "Blow on a horn for the Hodesh (New Moon)
On the Keseh (Full Moon) for the Day of our Hag (Feast)."
In the Bible, Feast (Hag) is a technical term which always refers to the three annual pilgrimage-feasts (Matzot, Shavuot, Sukkot; see Ex 23; Ex 34). New Moon Day (Hodesh) is never classified as a "Pilgrimage-Feast" so Keseh/ Hag can not possibly be synonymous with New Moon Day (Hodesh). It has further been suggested that Keseh refers to the Biblical holiday of Yom Teruah (Day of Shouting), which always falls out on New Moon Day. However, the Bible describes Yom Teruah as a Moed (appointed time) and never as a Hag (Pilgrimage-Feast) so Keseh/ Hag can not refer to Yom Teruah either.
Keseh is related to the Aramaic word "Kista" and the Assyrian word "Kuseu" which mean "full moon" This fits in perfectly with the description of Keseh as the day of the Hag since two of the three Pilgrimage-Feasts (Hag HaMatzot and Hag HaSukkot) are on the 15th of the month, which is about the time of the Full Moon!