Checks whether input time seems to be a timestamp.
Providing an input format will prevent ISO values without separators from being mis-interpreted as timestamps. Providing a format can also avoid interpreting a value like '2010' with a format of 'Y' as a timestamp. The 'U' format indicates this is a timestamp.
boolean TRUE if the input time is a timestamp.
public function inputIsTimestamp() {
return is_numeric($this->inputTimeAdjusted) && (empty($this->inputFormatAdjusted) || $this->inputFormatAdjusted == 'U');
}