I would hope his reaction would not ruin your day. I would first have to assume that you feel confidently enough to submit such a question. I have no knowledge of the condition of the relationship or the time involved. In a perfect world, that would be a great day to do as you plan. If he should feel that you have stolen "his day" by asking him to marry, then what you have there is a spoiled boy on your hands. Again, assuming he is in love with you, as you are with him, is he in a position to marry, how does he feel about the woman asking etc, do you know him well enough to predict his reaction?
Take a minute to give us some basic info about the two of you...how long, how old, first time marriage?, kids involved etc...
