Suppose a fellow realizes at 9:16AM that the Gra Zeman Kriyas Shema was at 9:14 and he never said Kriyas Shema yet. Is there any gain by saying it immediately even though it is past the later Zeman already or should he just say it in his Davening whenever he gets there. (sources)
1 Answer
1) If you are within a very short time you should say it immediately because Zmanim quotes are often rounded lechumra and may be slightly imprecise based on your exact location, elevation, and the outside weather. Plus there are slightly different opinions about how to calculate the time (how much of the sun needs to be above the horizon to be considered sunrise/sunset; if the hours of the first and second half of the day are calculated together or separately) so don't be so sure that the printed time you see is for sure right.
2) The Shulchan Aruch (OC 58:7) quotes an opinion that one who misses Shema in the morning or the evening should say a second Shema the following evening or morning. It seems most Achronim (Gra, Graz, Birkei Yosef, Mishna Berura, Aruch Hashulchan) reject this opinion, but it can't hurt.
This is all assuming you do recite it anyway later that day which should certainly be done (Kesef Mishna to Rambam Keriat Shema Chapter 1).