Rosh Chodesh

"Chodesh" in Hebrew means "fresh" and "Rosh" means "head"

So it is taken as the new beginning, in the Biblical calendar there is a new beginning every New Moon and that day was considered as a Sabbath a day of rest and reflection to start the month. 

It was also a day (as the Sabbath) when prophets were consulted.

Ezekiel 46;1-3