Related על חגיגה 35:1

[If] Shavuot fell on a Monday or on a Thursday or on a Friday or on a Sunday, [or] on any day of the week, Beit Shammai say, the "day of slaughter" is the next day. Beit Hillel say, there is no "day of slaughter" [rather, sacrifices are brought on Shavuot itself]. It so happened that Alexander (alt., "Alexa") died in Lod and the people of all the surrounding towns came to eulogize him. Rabbi Tarfon said to them, "Leave at once! We do not eulogize on a Festival!"

It is prohibited to fast immediately after the holiday of Shavuot. Ramah: And we do not say Tachanun from the beginning of Rosh Chodesh Sivan until the 8th day, which is after the post-holiday day (Hagahot Maimoni, Hil' Tefillah Umnagim). We have the custom to spread out plants on Shavuot in the synagogue and in houses, as a memory for the happiness of the receiving of the Torah. We have a custom everywhere to eat dairy food on the first day of Shavuot. And it seems to me that the reason is: It is like the two foods that are taken on the evening of Pesach, a reminder of the Korban Pesach and a reminder of the Korban Chagiga, so too we eat a dairy food followed by a meat food, and we bring with them two loaves on the table in place of the Mizbeach, and thus there will be a reminder of the two loaves that were brought on "The day of the Bikkurim."