The Mishna had stated: One who recites kerias shema after that time (the third hour) does not lose out, and is rewarded as if he was reading from the Torah.

The Gemora discusses the issue of reciting the brochos of kerias shema, when he is reciting shema after the proper time.

The Rosh cites the opinion of Rav Hai Gaon, who maintains that one may still recite the blessings during the fourth hour of the day. This is based upon the fact that the fourth hour is still the time that the morning prayers can be said according to Rabbi Yehudah. Other Rishonim hold that these brochos can be recited until chatzos (noon), for according to the Tanna Kamma, morning prayers may be said until then.

The Rambam in Hilchos Kerias Shema (1:13) rules that the brochos can be recited the entire day.

The Kesef Mishna explains the Rambam by asking the following question: