go-sql-driver/mysql · error

can't convert %T to time.Time

Error message

can't convert %T to time.Time

What it means

NullTime.Scan accepts only nil, time.Time, []byte (a date/time string), or string. Any other concrete type reaches the fallback and yields this error naming the offending type. It means the value being scanned into a NullTime is incompatible.

Solutions

1. Scan into the column's actual type (e.g. int64) and convert to time.Time yourself.
2. Write a custom sql.Scanner that converts the source type before assigning.
3. Ensure the source column is a MySQL DATE/TIME/DATETIME/TIMESTAMP so the driver yields a time.Time (with parseTime=true) or a scannable string.

Example fix

// before
var nt mysql.NullTime
rows.Scan(&nt) // column is BIGINT epoch -> error
// after (scan int, convert manually)
var epoch int64
rows.Scan(&epoch)
nt := mysql.NullTime{Valid: epoch != 0}
if nt.Valid {
    nt.Time = time.Unix(epoch, 0)
}

// Check the concrete type before scanning when the source is uncertain.
switch v := src.(type) {
case nil, time.Time, []byte, string:
    nt.Scan(v)
default:
    return fmt.Errorf("unsupported NullTime source: %T", v)
}

func isNullTimeScannable(v any) bool {
    switch v.(type) {
    case nil, time.Time, []byte, string:
        return true
    }
    return false
}

// NullTime.Scan returns this error; check it.
if err := nt.Scan(val); err != nil {
    // convert val to a supported type and retry
}

When it happens

Trigger: Scanning a numeric/decimal/integer column into a *mysql.NullTime, or calling nt.Scan with an int64/float64/struct value. E.g. a column stored as a unix epoch integer scanned directly into NullTime.

Common situations: Column-type mismatch (times stored as BIGINT epoch or DECIMAL); feeding a driver.Value of the wrong shape into Scan; schema drift.

Related errors

• cannot convert type: %T
• invalid timeTruncate value
• non-Value type %T returned from Value
• unsupported type %T, a
• unsupported type %T, a slice of

AI-assisted analysis of go-sql-driver/mysql@03d76c7e07 (2026-08-07). Data as JSON: /api/errors/966cc21fab4a54e9. Report an issue: GitHub.

Appendix: source

Thrown at nulltime.go:62

		return
	}

	switch v := value.(type) {
	case time.Time:
		nt.Time, nt.Valid = v, true
		return
	case []byte:
		nt.Time, err = parseDateTime(v, time.UTC)
		nt.Valid = (err == nil)
		return
	case string:
		nt.Time, err = parseDateTime([]byte(v), time.UTC)
		nt.Valid = (err == nil)
		return
	}

	nt.Valid = false
	return fmt.Errorf("can't convert %T to time.Time", value)
}

// Value implements the driver Valuer interface.
func (nt NullTime) Value() (driver.Value, error) {
	if !nt.Valid {
		return nil, nil
	}
	return nt.Time, nil
}

View on GitHub (pinned to 03d76c7e07)