I fertilize mine year-round, though with a light application - about 1/2 of what’s normally called for on the Miracle Grow package.
The change in the light really does make a difference, though.
Mine is in a south-facing window and the sun does all the work for me. I never move her, and with the angle of the sun changing from summer to fall, that seems to be enough of a change for her to trigger blooming.
Mine will bloom starting now (it’s in bud) and then in February and then sometimes in the spring again. I don’t move her outside for the summer, since she seems to be very happy right where she is, year-round.
My only south windows are on the front side of the house, where I would never get to see her. Our sunroom faces north, but there are windows on each side so it does have a lot of filtered light in there, just never anything direct. It is filled with houseplants. In the past, I’ve kept my Christmas cacti in there, and my first one lasted several years, but gave up the ghost last season. I probably should have repotted it a year or two before. This one was new last year. It only bloomed once. When it showed signs of life in the summer when I had put it in my reject pile, I decided to see if I could have success with it. I love a pretty Christmas cactus. I just need it to bloom some!