Calendar notifications stopped.

At 11:30 pm I had been getting a full screen reminder of my next days work hours, appointments, etc. And also on my drop down list. I relied on it as I work 2 part time jobs with varying days and hours, and also I didn't miss birthdays. But it has quit doing that! I have the Google and the android calendars on my Galaxy S5, but I use the adroid one. I have removed it and downloaded it again. Please help me get my notifications working again!!!