For example if I seal chicken in the morning by cooking it on just the outside, is it safe to cook that night all the way through if kept refrigerated during the day?
Searing chicken on the outside does not "seal" it. In fact, it is likely to bring the interior of the meat into the worst part of the danger zone (about 10-30° C above room temperature) and may actually reduce its safety factor.
If you seared it and put it directly back in the refrigerator, then it should still be under the 2-hour maximum for the temperature danger zone and safe to cook/eat. But be sure you cook it fully, up to the recommended 165° C; the previous searing doesn't count for anything, food-safety-wise.
If it sat around at room temperature after the searing for any significant length of time, throw it out.
Incidentally, if you want a good sear on any type of meat in addition to getting it properly cooked, the typical way to accomplish that is to either pop it into the oven for a bit after the initial sear, or to sear it after a slower-cooking method. I can't really see the point in searing a chicken several hours in advance.