Indigo.fko

I'm probably overthinking this, but out of curiosity, one if the program's I was accepted to said to respond by April 15 with my admissions decision; another said that I had until April 15. The wording of the former makes me think that I'd need to respond by end of day on the 14th, and as it's almost 9:00pm central, I don't have a way of contacting someone within the program for clarification. Is it likely that I should have through the end of day tomorrow to actually respond? I have one more waitlisted school I'd like to give a little more time to respond before I make my final decision. Many thanks!