That is what my daughter used to say when she got really excited about something. For example, when she was about 18 months old she wanted a little box opened and she couldn't do it so she asked her dad to open it. When she saw that he did she exclaimed Oh happy day!! and clapped her hands together. This is how I would describe my newest baby boy when he wakes every morning. It seems he greets each day with the attitude of "OH happy day!" We should all greet each new day with that attitude. The thought rolls through my mind "This is the day that the Lord has made, let us REJOICE and be GLAD in it!"