1. Even though the time for reading the Shema is until the end of the third hour of the day, the blessings of the Shema have the same laws as the Amidah prayer and may be said until the end of the fourth hour. (Shulchan Aruch and Mishne Berurah 58)
2. one who is unable to wait until the earliest time for reading the Shema in the morning, (e.g. if he is going on a journey and will be unable to concentrate properly,) may read it from daybreak. Even if someone is not forced, and reads it after daybreak, he has fulfilled his obligation, so long as he only does it on occasion, (not more than once a month), but if he does so regularly, he has not fulfilled his obligation and must read it again later. (ibid)
