New Moon = New Month. That was what the calendar was about for many ancient peoples.

Sod Ha’ibur is a website about the Hebrew Calendar. The first commandment given to Israel as a nation (as opposed to the individual patriarchs) was that of sanctifying the New Moon/month: 

החדש הזה לכם ראש חדשים ראשון הוא לכם לחדשי השנה.

This month shall be for you the beginning of the months, it shall be for you the first of the months of the year.

It will be a goal of this website to facilitate the keeping of this mitzvah with an added plus of understanding its history and science.