Time of sunrise, plus twelve, divide by two. That's zman krias shma. (Does not work during Daylight Savings.)
(Rav Baruch Epstein ob'm)
Eli points out that due to the Equation of Time, this is off a few minutes. Sorry, Reb Boruch.
AS OF DECEMBER 2013, NEW DIVREI TORAH WILL NOT BE POSTED HERE; THEY WILL BE POSTED AT MY OTHER WEBSITE, BEIS VAAD, beisvaad.blogspot.com Existing posts on this website will not be updated, and if there will be any new posts here, while they will be Torah-oriented, will not be yeshivish.