"One of Those Days"

Have you ever asked someone how they are doing and their reply was, "well, it's just been one of those days." What does that mean? I mean, seriously think about just how generic that statement is. There are 365 days on my calendar so which one of "those" days are they referring to? This weekend I took Ash on a date to Olive Garden, seen a couple of really good friends from Clear Water, Kansas along with 60 bikers for Bikes Blues and BBQ. I believe that was the ruffest looking crowd I've seen at Olive Garden. We had a blast. Was it one of those days? Last Sunday when I came home from Orlando Caleb began throwing up, followed by Ashley, then her mom all through the night, was that one of those days? I just get utterly confused that's all I'm saying. What if the next time someone says that to you your response is, "that's awesome I've had a great day too!" That should at LEAST confuse the mess out of them and will probably even make them laugh as you explain. Who knows could even change "one of those days."