A Month Isn’t Always a Month

The Daf has just finished studying the mitzvah of Pidyon Haben. It is a relatively rare mitzvah, with a number of conditions that must be met before it applies. It applies only when a woman’s firstborn child is a boy, and only if he was born naturally, not by C-section. It does not apply if the mother previously miscarried. Nor does it apply if the father is a Kohen or Levi, or if the mother is a bas Kohen or bas Levi. And, of course, it can only happen once in a woman’s lifetime.

There is an interesting connection between the rarity of Pidyon Haben and the recitation of Shehecheyanu.

The Ashkenazi custom is not to recite Shehecheyanu at a bris milah. The commonly cited reason is that the baby experiences some pain, making it inappropriate to recite a blessing of joy. However, Tosafos in Maseches Bechoros offers another explanation: a bris milah is not particularly rare, whereas Pidyon Haben is. Therefore, Shehecheyanu is recited at a Pidyon Haben.

The Torah commands that a firstborn son be redeemed after he reaches one month of age.

Other time periods are relatively easy to determine. A day consists of a period of daylight and darkness.

Interestingly, everyone knows exactly what a week is: seven days!

One fascinating indication that the seven-day week reflects the seven days of Creation is that, unlike the day, month, and year, the week has no astronomical basis. A day corresponds to the Earth’s rotation, a month roughly corresponds to the lunar cycle, and a solar year corresponds to the Earth’s revolution around the sun. Even a lunar year is based on twelve lunar cycles.

But there is no celestial phenomenon that dictates a seven-day cycle. Nevertheless, the seven-day week has become standardized throughout virtually the entire world, across cultures and civilizations. Its remarkable persistence, despite having no natural astronomical explanation, is a powerful testament to the account of Creation: the world was created in six days, followed by a seventh day of rest. The world’s societies ultimately adopted that same seven-day cycle.

The Torah, however, commands that Pidyon Haben be performed when the baby is one month old. As explained, the significance of a month is that it corresponds to one lunar cycle.

We know that Jewish months are either 29 or 30 days long. So, exactly how many days after a baby is born should his Pidyon Haben take place?

The Magen Avraham gives a seemingly simple answer: a month is 30 days. Thus, if a baby is born on March 1 at 3:00 p.m., his Pidyon Haben would be on March 31. Indeed, according to the letter of the law, the Pidyon Haben could even be performed on March 30 after nightfall, since that would mark the beginning of the 31st day.

But how did the Magen Avraham know that a month should be considered 30 days rather than 29?

The opinion of the Shach will shed some light on this question.

The Gemara records that the average length of a lunar cycle, from the time the moon first becomes visible until it disappears and reappears again, is 29 days, 12 hours, and 793 chalakim.

A chelek is a unit of time equal to 3⅓ seconds. Therefore, 793 chalakim amount to approximately 44.046 minutes. According to the Gemara, then, the average lunar cycle is 29 days, 12 hours, and 44.046 minutes.

Remarkably, more than a thousand years after the Gemara established the length of the lunar cycle as 29 days, 12 hours, and 793 chalakim, NASA, using modern astronomical calculations, arrived at virtually the identical figure: 29 days, 12 hours, 44 minutes, and 3 seconds. The difference between the two calculations is a mere one-third of a second! (The average varies from year to year. This was for the year 2000.)

In any case, how long should a Jewish month be? Twenty-nine days is too short, while 30 days is too long.

Now, students in elementary school love half-days. But Chazal weren’t particularly interested in having every month last 29½ days. That would get rather confusing! Half-days are for school, not the Jewish calendar.

The simple solution is to alternate the lengths of the months. Some months have 29 days, while others have 30.

The Shach, however, maintains that the month relevant to Pidyon Haben is neither 29 nor 30 days. Rather, it is the actual length of a lunar cycle: 29 days, 12 hours, and 44 minutes.

This creates some significant halachic differences between the Shach and the Magen Avraham.

As noted above, if a baby is born on March 1 at 3:00 p.m., the Magen Avraham would allow the Pidyon Haben to take place on the night of March 30, since that marks the beginning of the 31st day. The Shach, however, would consider that too early. According to the Shach, one would have to wait until 3:44 a.m. on March 31, when 29 days, 12 hours, and 44 minutes have elapsed since the birth.

Conversely, let’s say the baby was born on March 1 at 12:01 a.m. The Magen Avraham would still require waiting until the night of March 30. According to the Shach, however, the Pidyon Haben could already take place on March 30 at 12:45 p.m.

Practically speaking, this issue is treated stringently in both directions. We wait until the 31st day, as required by the Magen Avraham, and we also ensure that at least 29 days, 12 hours, and 44 minutes have elapsed since the baby’s birth, as required by the Shach.

Some explain that this is also the reason for the custom to perform Pidyon Haben only during the daytime: to ensure that the requisite 29½ days have passed.

But we still haven’t answered our original question: How did the Magen Avraham know that a month for Pidyon Haben should be 30 days?

The answer is that he began with the same assumption as the Shach: that a month is approximately 29½ days. However, the Gemara derives an additional requirement from a pasuk. The Shach understands this derivation to mean that the full 29½-day lunar cycle must elapse before the Pidyon Haben can take place.

The Magen Avraham, on the other hand, maintains that there would have been no reason to assume that Pidyon Haben could take place before the completion of that lunar cycle. Therefore, the drasha must be teaching us something more: that we must wait an additional amount of time, until a full 30 days have passed.

Apparently, when it comes to school, everyone loves a half-day. But when it comes to Pidyon Haben, whether you’re following the Shach or the Magen Avraham, you can’t cut corners. Every minute counts!