I remember from way back when calling the time number all the time. People now just turn on CNN and look at the time on the screen. The number to call can vary depending on where you live. Please see http://www.phworld.org/sounds/modern/timetemp/
You don't say where you are. It has been discontinued in California where it used to be 853-1212 from any area code in the south part of the state and popcorn in the north. Your mobile phone should be quite accurate.