arib | (no subject)

So, why is it that the molad and rosh chodesh aren't lining up anymore?

Could you please explain this to those of us who have no idea what you're talking about?

Molad: prediction, based on a formula going back about two thousand years, of when the astronomical new moon will occur.

Rosh chodesh: the first day of the new month according to the Jewish calendar that was established at the same time.

There's a pretty good explanation at Torah Tidbits.

I assume it's a side effect from trying to ensure that certain holidays do not fall on certain days of the week, but that's just a guess.