"You shall count seven complete weeks after the day following the Shabbat from the day you brought the omer as a wave offering until the day after the seventh week when there will a total of fifty days" (23:15-16). The holiday of Shavuot marking the wheat harvest lacks its own independent date, its celebration being linked to Pesach. We tend to think of the linkage between the physical and spiritual freedom, the means and the end if you like. The purpose of the exodus was to receive the Torah and thus Shavuot is really the completion of Pesach. While this is undoubtedly true, nowhere is this to be found in the Torah itself. The Talmud was not even certain the exact date we received the Torah; it is really irrelevant anyway as that first covenant was broken with the building of the golden calf. The date we received the Torah that we observe today was Yom Kippur, not Shavuot. Shavuot in the Biblical text is purely an agricultural holiday, a one day pause in the middle of the busy summer season to express our gratitude to G-d.
The calenderic dependence of Shavuot on Pesach raises the question of why we in the Diaspora must observe a second day of Yom tov for Shavuot. As is well known the second day of Yom tov was instituted due to the uncertainty over which day had been declared the first of the month (Rosh Chodesh). While it might have taken more than two weeks to find out this information - hence the need for an extra day of Pesach - seven weeks later all was known. In practice there was never any doubt as to which day was actually Shavuot and thus no need for a second day of Yom tov.
The whole notion of the second day of Yom tov in general has other anomalies. If we are going to be consistent we should have a second day of Yom Kippur as the Diaspora communities were, at the tenth of the month still unsure as to the exact day of Rosh Chodesh. And if Yom Kippur is only one day surely five days later there is no reason to have two days of Sukkot! Furthermore Rosh Hashanah is observed for two days even in Israel - it would be a misnomer to call it the "second day Yom-tov of the Diaspora". While individually we could perhaps offer answers to each one of these questions - it would be to difficult too fast for two days of Yom Kippur for instance - the fact that there are more exceptions to the rule than the rule itself is quite strange. Surely the rule needs some re-examining. It should come as no surprise that one of the earliest innovations of the Reform movement was the abolishment of the second day of Yom -Tov. Why is it that the Halacha is so insistent on maintaining the second day?
Being in the midst of Yom Haatzmaut - we celebrated it on Thursday but the fifth of Iyar is not until Shabbat, a three day Yom Tov if you may - perhaps we can offer a "Zionistic" approach. When all is said and done what we have is the three pilgrim festivals of Pesach, Shavuot and Sukkot having an extra day in the Diaspora whereas the Yamim Noraim - Rosh Hashanah and Yom Kippur are celebrated on the same days both in Israel and abroad. It is Pesach, Shavuot and Sukkot that celebrate our ties to the land of Israel . Chag haAviv, Chag HaKatzir and Chag HaAssif celebrate the agricultural cycle of the land of Israel . We perform the mitzvah of aliyah L'Regel , travelling to Jerusalem together with thousands of other Jews. They are the nationalistic holidays of Jewish people and as Rav Shimshon Raphael Hirsch points out they are the only ones mentioned in Sefer Devarim - the book about preparing to enter the land of Israel . It is as if Jews living in the Diaspora need an extra day to begin to appreciate the meaning of these days - because living outside of Israel we can not fully observe them. The extra day makes clear the qualitative distinction between life in Israel and life in exile.
The Yamim Noraim, on the other hand, are holidays that concentrate on our personal relationship to G-d, where we focus on self evaluation and improvement. In this need for Tehsuva there is no difference where we reside - Yom Kippur is Yom Kippur. While the Jewish people are one there is only one land of Israel . Shabbat Shalom .