It says in Masechet Megillah
אָמַררַבָּהבַּרבַּרחָנָהא״ריוֹחָנָןזוֹדִּבְרֵיר״עסְתִימְתָאָהדְּדָרִישׁזְמַןזְמַנָּםזמניהםאֲבָלחכ״אאֵיןקוֹרִיןאוֹתָהּאֶלָּאבִּזְמַנָּהּמֵיתִיבִיא״ריְהוּדָהאֵימָתַיבִּזְמַןשֶׁהַשָּׁנִיםכְּתְּיקְנָןוְיִשְׂרָאֵלשְׁרוּיִיןעַלאַדְמָתָןאֲבָלבַּזְּמַןהַזֶּההוֹאִילוּמִסְתַּכְּלִיןבָּהּאֵיןקוֹרִיןאוֹתָהּאֶלָּאבִּזְמַנָּהּרַבִּייְהוּדָהאַלִּיבָּאדְּמַאןאִילֵימָאאַלִּיבָּאדר״עאֲפִילּוּבַּזְּמַןהַזֶּהאִיתָאלְהַאיתַּקַּנְתָּאאֶלָּאלַאואַלִּיבָּאדְּרַבָּנַןוּבִזְמַןשֶׁהַשְּׁנַיִםכְּתְּיקְנָןוְיִשְׂרָאֵלשְׁרוּיִיןעַלאַדְמָתָןמִיהָאקָרֵינָןתְּיוּבְתָאדְּרִבִּייוֹחָנָן
Rabbah bar Bar Chanah said that Rabbi Yochanan said: This rule statedin the Mishnah are the words of Rabbi Akiva, the anonymous author,[He's called this because when Rabbi Yehuda HaNasi compiled theMishnah, and didn't mention the name of an opinion's author, it wasusually Rabbi Akiva's opinion.] who interpreted 'time', 'their time',and 'their times'. But the Sages say: The Megillah is only read in itstime [the 14th and 15th of Adar]. They raised an objection: RabbiYehuda said: When does this rule apply? When the years are properlyfixed [when there's a Beis Din that fixes new moons and leap years],and the Jewish people inhabit their Land. But these days [literally:at this time], since people look at it [they count 30 days from Purimto Pesach, since Adar always has 29 days], it's read only in its time.Which opinion is Rabbi Yehuda following? If I say he's speakingaccording to Rabbi Akiva, this can't be, because according to him theenactment [that the Megillah may be read on the 11th, 12th, or 13th]is even in effect until today. Rather, isn't it that he's speakingaccording to the Rabbis, and even according to them in any event, weread on the other days when the years are properly fixed and theJewish people inhabit their Land. This is a refutation of RabbiYochanan.
The reason why we reject R' Yehudah's answer is because it doesn't follow R. Akiva or the Chachamim's answer. But why can't R. Yehudah have his own opinion?
