GOD GAVE US HIS 'LUNAR CALENDAR' SO THAT WE WOULD NEVER BE CONFUSED......
Isaiah 66:23
"And it shall come to pass that from one NEW MOON TO ANOTHER (one month to another month), and from one Sabbath to another (one week to another week), ALL flesh shall come to worship before Me, says the Lord."
Therefore we are told that each of God's months begins on the New Moon day which is the 1st of the month - the 1st of each and every Biblical month for eternity. You can readily see that man, over time, has corrupted God's planned holy calendar for his own convient purposes. Our modern calendar is not a Scriptural calendar in any way. Modern Christians and Jews do not know the true Sabbaths of the Lord. The only way to observe God's ordained calendar is to observe the day of the new Moon each month and call that day the 1st of the month. You can bet God is NOT observing any part of the modern calendar of modern man.
According to Isaiah 66:23 God wants His people, that would be us, to worship Him on the day of the New Moon which is always the 1st of the true month, and on the true Sabbaths of the month which follow the New Moon every seven days thereafter throughout each month.