Halacha:

Shavuot 

Machshava:

Shavuot,  Torah 

Holidays:

Yom Tov Sheni 

References: Rosh Hashana: 6b ,  Shabbat: 86b ,  Shabbat: 87a  

Description

How can there be a machlokes about the date of Matan Torah, and are we celebrating on the wrong day?! Halachic and Hashkafic takeaways from this unique aspect of Shavuos. (Sources Attached; See also Shu"t Chasam Sofer, OC 145)