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.
In the year 2019 CE the months begin on the following dates. We celebrate each new moon in the beginning of the first day of the month, which is at sundown the evening prior to the given date.