This is how I make my planner horizontal that is vertical. It is very easy. I like to use my computer for this. I use Pages on my Macbook but you can use any word, works or any program. I just put in the dates in the font and color I like as you can see. I will do three weeks on a page.
Then I print them out and cut into strips, trim and glue them on.You could of course just write them in, but i wanted it neater for me.
As you can see I just cut 1" strip from a magazine and glued it over the top dates. Any kind of papers will do. I just happen to like pictures a lot.