What did people say in Shemoneh Esrei and Kiddush of Shavuos when it didn't fall out on the 6th of Sivan?

Question

During Shemoneh Esrei and Kiddush of Shavuos, we describe the Yom Tov as "this day of the holiday of Shavuos, the time of giving our Torah" (יום חג השבועות הזה זמן מתן תורתינו).

Before we had a fixed calendar, it was theoretically possible for any month to have either 29 or 30 days (unlike our current calendar wherein only Cheshvan and Kislev have variable lengths). If both Nissan and Iyar were to have 30 days, Shavuos (which is fixed at 50 days after the first day of Pesach, rather than being on a specific day on the calendar, as per Vayikra 23:16-21) would fall out on the 5th of Sivan. According to no opinion in the Gemara (Shabbos 86b) did the giving of the Torah occur on the 5th of Sivan.

What was said during davening and Kiddush of Shavuos those years? Did they still say "the time of giving our Torah," since it's the same time of year? Did they say something else ("the time of preparing for giving our Torah" maybe)? Did they say nothing at all?

Answer 1

Two basic answers exist to this question:

1. In reality, when the calendar was decided by testimony of the new moon, this phrase probably did not exist in the prayers. Maseches Sofrim 19:4 writes:

   בחג שבועות אומר ביום טוב מקרא קודש הזה וביום חג השבועות הזה וערבית שחרית ומנחה שוין בתפלות

   In fact, the Ritva (to Shabbos 86b) and Rivash (Shut no. 96) imply that we never associated Shavuos with the day of the giving of the Torah until the calendar was fixed so that Shavuos always fell out on the anniversary of matan Torah.

2. Many (too many to list, but the earliest one was probably the Hadar Zekeinim al haTorah, from the Tosafos) explain that when the prayer says "זמן מתן תורתנו" it is referring not to a single day, but to a time frame that could span several days. Although this is also the formulation used for Pesach and Sukkos, that is because those holidays last for several days, and so we could not say יום חירותנו or the like. But because Shavuos is only one day, we should have been able to say יום מתן תורתנו, but we do not, because we are referring to the 'general time of year' instead of the actual anniversary date, which is not always on Shavuos. Torah Temimah (Shemos 24:16) adds that the "giving of the Torah" itself was a process that took several days, so we properly refer to it as the general "time" at which the Torah was given

Answer 2

Rav Yehoshua ibn Shu’ib, Rabbi Mordecai ben Abraham Benet, and the Mateh Moshe (Laws of Shavuot 690) explain that for this reason the more general word 'time' is used instead of the more precise 'day' (the term usually used to refer to a one day holiday), because it hasn't always been the exact day, but it always is in the general time frame of Matan Torah. According to this opinion the nusach has always been זמן מתן תורתינו.