To my programmer friends, how long would it have taken to answer this question using Google and StackExchange. There was a bug in this one line of code, a call to new Date () in JavaScript, that was behaving as if months were not 0-based, which they are known to be. The problem: I was specifying the day as 0 and month, correctly, but the day had to be 1 in order for it to work and without thinking I had specified it as 0.