presto-main/src/main/java/io/prestosql/operator/scalar/DateTimeFunctions.java/DateTimeFunctions/currentTimestamp
class DateTimeFunctions:    @Description("current timestamp with time zone")
    @ScalarFunction(value = "current_timestamp", alias = "now")
    @SqlType(StandardTypes.TIMESTAMP_WITH_TIME_ZONE)
    public static long currentTimestamp(ConnectorSession session)
    {
        return packDateTimeWithZone(session.getStartTime(), session.getTimeZoneKey());
    }