Why do we (in Orthodox congregations) announce the ‘molad’ the Shabbat before a new month? Since our calendar is fixed, what difference does it make?
Take this past week as an example. In our synagogue we announced that the molad was some time on Sunday morning (forgive me for not remembering the exact time). In that case, Rosh Chodesh should be on Monday. But it’s not. The new month of Sivan begins on Tuesday. So why bother announcing something that has no bearing on anything and which at best is just a vestige of a prior practice and at worst may serve to confuse people as to which day to commemorate the new month?