A: According to the Hebrew calendar, a month starts with a new moon. While there are express and clear commandments in the Bible to celebrate today God's weekly Sabbath and His annual Holy Days, there is no command in the Bible, enjoining us to celebrate today the beginning of the new months -- or new moons. The early New Testament Church continued to keep and celebrate the weekly Sabbath and the annual Holy Days, but we do not have any Biblical record indicating that they celebrated new moons. (In Colossians 2:16, Paul does not speak about "new moons" in general, but about "a new moon" -- referring specifically to the Feast of Trumpets, the only annual Feast day which falls on a new moon.)
In ancient times, some assembled on the occasion of each new moon, with the blowing of trumpets, to signify the beginning of a month (Numbers 10:10). Calendars were not available to everyone in ancient Israel the way we have them today. Rather, the priesthood was entrusted with the responsibility to determine and make known to the people when a new month would start.
Some form of ceremony took place on the day of a new moon, to let the people know that a new month had begun. Some used the occasion to have a feast on that day (1 Samuel 20:5, 18, 24) -- although, as mentioned, the Bible nowhere commands that new moons have to be celebrated in that way. We read that offerings were to be given on new moons (2 Chronicles 31:3; Ezra 3:5; Nehemiah 10:33), but such offerings (sacrifices) are, of course, no longer required today, either. Even in ancient Israel, we do not find that God commanded the celebration of new moons per se -- that is, unconnected to the giving of sacrifices. On the other hand, we do find that the weekly Sabbath and the annual Holy Days were in force before the sacrificial system was introduced, and that they are to be kept today, even though sacrifices are no longer necessary (Our booklet, God's Commanded Holy Days, on the Sabbath and the annual Holy Days proves this fact from the Bible.).
It was, however, necessary in ancient times to somehow mark the beginning of the month, as it was not always easy for everyone to independently observe the new moon, due, perhaps, to clouds or heavy rain. By actually conducting a certain ceremony at the appearance of a new moon, the general population was sufficiently informed and enabled to prepare for any approaching seasons or annual Holy Days, which are counted and determined by the appearance of the new moon. For instance, as mentioned, the Feast of Trumpets is celebrated on a new moon (compare Psalm 81:3) -- the first day of the month. Ten days later, the Day of Atonement is kept, and the Feast of Tabernacles begins fifteen days after the Feast of Trumpets.
It appears that in the process of time, the ancient celebrations of new moons had reached proportions that were not accepted by God. He tells us in Isaiah 1:14, "Your New Moons and your appointed feasts My soul hates; They are a trouble to Me, I am weary of bearing them." Apparently, new moons were even celebrated in the same way as Sabbaths are to be kept -- with prohibitions to engage in merchandising (compare Amos 8:5). However, such a prohibition for new moons cannot be found in Scripture.
Today, it is not necessary to mark the beginning of each new month with feast celebrations, the blowing of trumpets, or an assembly. Calendars are available which list, well in advance, the dates of the appearance of each new moon throughout the year.
It is true that the Bible indicates that at the beginning of the Millennium, new moons will be kept in conjunction with the bringing of sacrifices (Ezekiel 45:17, 46:1, 3, 6; Isaiah 66:20-23). Why God will reintroduce a system of sacrifices in the Millennium, connected with new moon celebrations, the Bible does not explicitly say. Our free booklet, "And Lawlessness Will Abound..." suggests a distinct possibility.
It is clear from Scripture, however, that God does not command His people today to celebrate new moons.
"You are the light of the world. A city that is set on a hill cannot be hidden."-Matthew 5:14