Apple's iOS 6 operating system for iPhone, iPad and iPod touch has a Do Not Disturb feature that silences all incoming calls and alerts when they ring the first time. If the person calls in again (meaning it may be urgent), the call goes through. This feature is very useful at night and can be scheduled to go on and off at certain hours. But there was a hiccup in the new year.
For some people, the feature did not turn off when they woke up in 2013. This meant that calls coming in the day would be silenced as well unless you realize that the scheduled Do Not Disturb is still on. I don't use the feature, so I haven't experienced it. But those who do, go into the settings and check to see if the switch is still in the On position. If the feature is on, you will see a moon icon in the status bar as usual.
As if this was not enough, Apple awkwardly released a new iPhone ad touting this very feature that had gone wonky around January 1st, 2013. They had most probably scheduled the release of this TV spot and it happened to be around the time many users were affected by this bug. The ad, embedded below is titled "Dream".
A time-related bug in iOS isn't new. Around January 1st 2012, some users' alarms had failed to go off.