Gemara (Rosh Hashanah 18b): It was stated, "Rav and Rabbi Chanina said, 'The Scroll of Fasting (Megillat Taanit) has been abolished.' And Rabbi Yochanan and Rabbi Yehoshua ben Levi said, 'It was not abolished.'" (19b) And the law is that it was abolished; and the law is that it was not abolished! There is a difficulty from [one] law to [the other] law!?! It is not difficult. Here it is about Chanukkah and Purim; there it is about the other days.