presto-main/src/main/java/io/prestosql/operator/scalar/DateTimeFunctions.java/DateTimeFunctions/toUnixTimeFromTimestampWithTimeZone
class DateTimeFunctions:    @ScalarFunction("to_unixtime")
    @SqlType(StandardTypes.DOUBLE)
    public static double toUnixTimeFromTimestampWithTimeZone(@SqlType(StandardTypes.TIMESTAMP_WITH_TIME_ZONE) long timestampWithTimeZone)
    {
        return unpackMillisUtc(timestampWithTimeZone) / 1000.0;
    }