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;
	}