In the Wikipedia article on Rosh Chodesh it says that historically it had much more importance, why did it change? Do Rabbinic sources or commentators attest to this? Is there evidence during the times of the Beit Hamikdash that Rosh Chodesh was a holiday where melacha largely ceased? And what changed that makes it into the very minor thing it is nowadays? Did it have a different halachic status during the standing of the temple?