In CAD and CALP you can make your RM any meal of the day you want. The problem with making it breakfast is that you then have to face temptations for the rest of the day. It is much easier to say no to unallowed foods when you know you're going to have your favorite foods for dinner.

On the other hand I have often had breakfast for dinner because that's what I want for my RM.

Whichever time of the day you select for your RM, you must keep it there, except for special occassions, as your body gets into a rhythm. If you move it sporadically, you throw your insulin levels off and can gain weight.