I didn't really resolve it but I do at least have a somewhat functioning calendar now. I changed colors for my background, themes, etc. I did this until I found it worked. I also pulled down the calendar from the top of the page to expand the dates to see the events(they aren't viewable the way the calendar resets to). I hope this helps.
I tried different themes, made no difference, tried to find a way to change font colour, bizarrely no options to do this appear to exist. So i now play hit the screen around where i used to in order to brjng up the time and date option to enter details. Pretty much same when trying to read items.
I had the same issue. Try to find out the name of your theme. If you are lucky (I was) your theme allready has an update for this Samsung update. After updating your theme the "white letters on white background" issue will be gone. Otherwise you will need to choose another theme or wallpaper.