}
	return FromTimestamp(t.Add(duration)), nil
}

// dateDiff computes the difference between two times in terms of the
// `timePart` which can be years, months, days, hours, minutes or
// seconds. For difference in years, months or days, the time part,
// including timezone is ignored.
func dateDiff(timePart string, ts1, ts2 time.Time) (*Value, error) {
	if ts2.Before(ts1) {

			return -1, nil
		}
	}

	// Try to parse as a number of months
	if !strings.HasSuffix(s, "m") {
		return -1, errors.New("unknown format")
	}

	months, err := strconv.Atoi(strings.TrimSuffix(s, "m"))
	if err != nil {
		return -1, err
	}

	if months < minimumBitrotCycleInMonths {
		return -1, fmt.Errorf("minimum bitrot cycle is %d month(s)", minimumBitrotCycleInMonths)
	}

		// Testcase index 20
		{30 * 24 * time.Hour, "my_download_url", "1 month before the latest release"},
		{31 * 24 * time.Hour, "my_download_url", "1 month before the latest release"},
		{61 * 24 * time.Hour, "my_download_url", "2 months before the latest release"},
		{360 * 24 * time.Hour, "my_download_url", "1 year before the latest release"},

		"sum(2 + s.id)",
		"sum(t)",
		"avg(s.id[1])",
		"coalesce(s.id[1], 2, 2 + 3)",

		"cast(s as string)",
		"cast(s AS INT)",
		"cast(s as DECIMAL)",
		"extract(YEAR from '2018-01-09')",
		"extract(month from '2018-01-09')",

		"extract(hour from '2018-01-09')",
		"extract(day from '2018-01-09')",
		"substring('abcd' from 2 for 2)",
		"substring('abcd' from 2)",
		"substring('abcd' , 2 , 2)",