God marks the beginning of each new month with special sacrifices (Nu 28:11-15) and invites us to worship together before Him. (Eze 46:3) This cyclical pattern is intrinsic to God’s kingdom (Is 66:23), so the Apostle Paul encourages believers to observe these appointed times today. (Col 2:16-17) This helps keeps us all in step with God and His calendar.
We celebrate each new moon in the beginning of the first day of the month, starting at the 1st sunset in Jerusalem on or after the astronomical new moon. (If the conjunction is between sunset and midnight, add two days to the conjunction date, else add 1 day)
In the year 2020 CE, the months begin on the following dates, starting sundown the evening prior to the given date.