ios7 software update failed

I keep trying to download ios7 to my iPhone 4, but whenever I do it keeps saying the software update failed? Also when I check for updates on my iTunes it says that my iPhone is up to date on ios 6.1.3 (even though ios7 came out at 6 o'clock.)

Is the software update failure a widespread error or is it just on certain iPhones? Is there any way to fix this?

Thanks.