Rabbi Shimon Kayara composed the Halachot Gedolot in year 1052 of the Seleucid era, which is year 4500. He was not ordained as a Gaon, so wrote the Ra'avah. In the introduction to the Sema"g it is written that Rav Yehuda Gaon [(bar Mar Rav Nachman, see above year 4515)] composed the Sefer HaBehag. [(And Shada"k page 36b writes as it appears in Mordechai, chapter Elu Megalchin, he was an old blind man and Rabbi Shimon Kayara his son also composed Halachot Gedolot in year 4510.

And so too Yuchsin in the order of tradition from the Rama"n).] In the introduction, the printer of Sefer HaBehag rejected the words of the Sema"g because it is found in the responsa that in tractate Berachot, Akashei Lei Rabbanan to Mar Rav Yehuda Gaon, so it appears he is not the author, end quote.

However, one can say the words of the Sema"g are valid because we find two Rav Yehuda Geonim: one was Rav Yehuda bar Nachman, and one was Rav Yehuda bar Ochna'i [(Tzemach David). (See above year 4519). And there is another Rav Yehuda Gaon (see above year 4480), and in Siftei Yeshenim it is written that some attribute it to Rav Yosef 'good eye' and Rashi Sukkah (38 p.b) and so too Rav Yehuda Gaon, author of Halachot Gedolot.] In this year there was a great earthquake in the city of Constantinople for a whole year.

And in year 4510, 60,000 people died of plague inside the city [(Tzemach David, Part 2)].