Hello,<br/><br/>1.Once upon a time there was a beautiful princess.<br/><br/>2.Once upon a time, everyone knew each other in this town and nobody bothered locking their doors.<br/><br/>Here in (1) there is no comma(,) after "once upon a time" while in the (2) there is comma.<br/><br/>I am little bit confused about this comma usage in this context.<br/><br/>Could anybody here clear it?<br/><br/>Thanks.