This function returns a string primitive representing the current UTC time value.
When the Date() constructor is called as a function rather than in a new expression, it returns a string representing the current time (in UTC time). Note that when calling it as a function the arguments are all ignored and it is not equivalent to calling the Date() constructor in a new expression at all.
ECMA 262 edition 2 - section - 18.104.22.168
ECMA 262 edition 2 - section - 15.9.2
ECMA 262 edition 3 - section - 15.9.2