code: public static function setFakeTime( $fakeTime ) {
  		if ( is_string( $fakeTime ) ) {
  			$fakeTime = (int)static::convert( TS_UNIX, $fakeTime );
  		}
  
  		if ( is_int( $fakeTime ) ) {
  			$fakeTime = function () use ( $fakeTime ) {
  				return $fakeTime;
  			};
  		}
  
  		$old = static::$fakeTimeCallback;
  		static::$fakeTimeCallback = $fakeTime ? $fakeTime : null;
  		return $old;
  	}
docs: Set a fake time value or clock callback.
  
  @param callable|string|int|false $fakeTime a fixed time string, or an integer Unix time, or
  a callback() returning an int representing a UNIX epoch, or false to disable fake time and
  go back to real time.
  
  @return callable|null the previous fake time callback, if any.