Night time icon won't go away during the day

I received an iPhone 4S for Christmas and so far it's been working fine. However, I am experiencing one small yet persistent bug. During the day, the little crescent moon icon that denotes the night hours next to the time at the top of the screen won't go away. The time will say something like 11:48 AM, but the moon icon will still appear next to it. I've tried manually changing the time and resetting the time zone, but the icon stays. It's a small gripe, but nevertheless one that I'd like to fix. Any help is appreciated.

Thanks!