This Shabbat, which is Rosh Chodesh Nisan, and which is when we read Parshat HaChodesh, serves as a good example to point out an important irony of our Calendar and to look at its messages.
Last Shabbat, we announced that the molad - the New Moon - of Nisan will be next Shabbat (that's this Shabbat) at 3 hours, 53 minutes, and 4 parts (chalakim, one of with is 3 and a third seconds). That translates to 3:32am Israel time.
In fact, the real, actual, astronomical molad - the New Moon, is almost 12 hours later, at 3:11pm on Shabbat afternoon.
The molad we announce is based on the average time for the Moon to go through the cycle of its phases, which is 29d 12h 44m 1p.
As we've explained in the past, the actual time of a lunation (that's what it's called in English) varies from month to month. This is so because the distances between Earth and Moon, and Earth- Moon and Sun vary, and those differences affect the velocity of Earth and Moon in their orbits, thereby affecting the timing.
Don't worry if you didn't follow that, just know that the average molad deviates from the actual molad up to half a day or more on either side, earlier or later.
Be clear: Without a Sanhedrin, our calendar is based on the average calculations. The actual molad (which we include in the Word of the Month box for every M'vorchim) is of academic interest only. THAT IS, until the Sanhed- returns to Lishkat HaGazit. Then, IYH may it be soon in our time, the average molad will not be used, and the actual molad will be used by the Sanhedrin (with other factors) to determine whether the Moon will be visible or not on the night following the 29th of a month. We'll spare you futher details at this point.
Now for the irony... and its message.
When G-d gave us (via Moshe and Aharon) the mitzva of HaChodesh Hazeh Lachem, His intention (so to speak) was that months should begin from the beginning of the Moon's cycle - i.e. from when the Moon is between the Earth and Sun and cannot be seen. From there, in the course of the month, the Moon goes through its phases, waxing until Full Moon and then waning until it once again it cannot be seen.
The problem, as Moshe pointed out to G-d (so to speak), is that if LACHEM means that G-d was giving over to us the sanctification of the month, we would not be able to see the beginning of the Moon's cycle and would not be able to sanctify it properly.
G-d's response to Moshe was to agree to wait for a number of hours until the Moon would be visible to people, and then they (we) would be able to testify to the first visibility of the lunar crescent and the Sanhedrin would be able to sanctify the month.
This was facilitated by G-d's showing Moshe the form of the first visibility of the Moon and saying to him - KAZEH R'EI V'KADEISH, when you see it like this, sanctify (the day as Rosh Chodesh).
Now go back to our current calendar. Notice that the molad (both average and actual) of Nisan occurs on Shabbat, which is Rosh Chodesh Nisan. Exactly as G-d had planned - EXCEPT for one important thing - having Rosh Chodesh on the day of the molad (or shortly after it) happens, and can only happen, when we are not involved 'hands on' with the process. Without a Sanhedrin, all we do is the numbers. We calculate and we determine the calendar by the formula passed down to us by a Sanhedrin of long ago. We are passive. And that's NOT what G-d wants. It is a Plan B brought about by OUR misdeeds that led to the destruction of the Beit HaMikdash, the Exile and Dispersion, and (generations later) to the demise of the Sanhedrin.
The Israel New Moon Society, which practices the process of sighting the L'VANA B'CHIDUSHA, the first visibility of the lunar crescent, sent out an email to its members to look for the Moon on Sunday evening. If we had a Sanhedrin, Rosh Chodesh Nisan would most likely be on Monday - two days later than the originally intended beginning of the month. But that would be fine with HKB"H (so to speak), because it would come along with His preferred Plan A - that which involves the active participation of B'nei Yisrael in the process of Sanctifying Time (as He had done with Shabbat)
So that's the irony. Plan A, HaShem's preference, turns out to be less accurate (except it is not inaccurate because G-d 'changed' the set up), less efficient (clouds can obscure visibility, witnesses can be mistaken in what they thought they saw...) but it fulfills LACHEM.
This is so much HaShem's Will, that He has His Shabbat stand aside so that potential witnesses who think they MIGHT have seen the L'VANA B'CHIDUSHA can travel to Jerusalem on a Friday night in order testify. May we see the restoration of KIDDUSH HACHODESH - Plan A, speedily in out time.