iPhone 4 running iOS 5 (likely reproducible on iPhone 3GS/4S) NOTE: I can also confirm that this bug is reproducible on iPhone 4 (running iOS 5). Not only did the bug happen to me, but it also happened to someone else who followed my own instructions for adjusting the date and time (to accommodate our lack of timezone change). I'm posting this here in the main page because as far as I can surmise I am the only one to have experienced this bug. Yes, I'm well aware of the usual timezone bugs (where the phone doesn't change to the correct time). This is something different. Here is how the bug happened. I live in a timezone (Regina, Canada) that doesn't switch to daylight savings time. As such, a few days ago I woke up to my phone having the wrong time. Having to adjust the time by an hour, I simply went to settings and manually bumped the time back an hour (so that it would be correct). I didn't notice right away (indeed not even that day), but several things happened to my phone: The first thing I noticed was that my twitter feed (in the Tweetbot app) was showing every new tweet as being posted an hour ago. Indeed, this time signature error was subsequently noticed in every app. The second thing I noticed was that iMessages stopped working. In a vain attempt to address the iMessage problem, I deactivated iMessages in my settings. As a result, I was unable to reactivate iMessages (as a result of this bug). The third thing that happened was that I was unable to make FaceTime calls. Thankfully, FaceTime actually gave me a notification that explained the problem. It said something to the effect of "in order to make FaceTime calls you must adjust your date and time settings." It was at this point that I started to put it together. The timestamp errors, the iMessage failure, the FaceTime problems were all connected my having manually changed the time on my iPhone. Since it's quite possible that someone else will find themselves in a similar position, here is how to fix the problem: 1) Settings > General > Date and Time > and then; Turn on the Set Automatically button: the iPhone will select a timezone near you (it may or may not be your correct time zone) Turn off the Set Automatically button. 2) Tap Time Zone, and then search for your time zone. Select your time zone (your iPhone should now be showing "Time Zone: _____ (your time zone)" as well as displaying the correct time on the top bar. 3) Turn your iPhone off and then turn it on again. Now, your iPhone should be displaying the correct time (respecting your time zone change - or lack of change), all of your time signatures for tweets and other apps should be working properly, and more importantly iMessage and FaceTime will work again (in my case, I was able to reactivate iMessages only after the bug fix). If anyone else has experienced this buy please let me know. I plan to submit a bug report to Apple so it would be nice to hear from others who have experienced the same bug.