How do I move pictures to add them to a different grouping in my photo library on my MacBook

no, I don't mean album. All my pictures are arranged according to dates. I want to drag a picture or a series of pictures form one date to another.

No, I want to move pictures from one date to another. I used to click on the picture and drag it, but that doesn't work?

Is a macbook air a smart album? And if so does that mean I cannot move photos from one set to another?

Also, do you know how to add people to the "People" in my Library?

When I take a picture or pictures they are stored in Iphotos by the date I took them.

I want to drag pictures from one date and include them in pictures from a different date.

Thank you Terence