# DateTime64

`DateTime64` represents an instant with configurable fractional-second precision and a declared timezone. Use it for event times that require milliseconds, microseconds or nanoseconds.

## Syntax

```text
DateTime64
DateTime64(P)
DateTime64(P, 'timezone')
TIMESTAMP
TIMESTAMP(P)
TIMESTAMP(P, 'timezone')
```

## Parameters and range

* `P` — The number of fractional-second digits, from 0 through 9. `DateTime64` defaults to 3; the `TIMESTAMP` alias defaults to 6.
* `timezone` — An IANA timezone name. The default is `'UTC'`.

The calendar range is 1900 through 2299, further limited by signed 64-bit tick capacity. Precision 9 reaches its upper tick limit in 2262.

## Input units

Integer input is a count of ticks at the declared precision. At precision 3, `1234` means `1.234` seconds after the Unix epoch. Decimal input instead expresses epoch seconds. Text is interpreted as local date and time in the declared timezone.

Casting to a numeric type returns epoch seconds; a `REAL` or Decimal target can retain fractions. Lowering precision discards fractional digits while remaining in the containing tick, including for times before 1970.

As with [DateTime](https://coordinatordb.com/docs/reference/data-types/datetime), ambiguous or nonexistent local times are rejected. Text with no clock time denotes local midnight.

## Examples

### Preserving microseconds

```sql
SELECT CAST('2025-03-05 12:30:00.123456' AS DateTime64(6, 'UTC'))
FORMAT csv;
```

```text
"2025-03-05 12:30:00.123456"
```

### Integer ticks and decimal seconds

Both values below represent the same instant:

```sql
SELECT CAST(1234 AS DateTime64(3, 'UTC')),
       CAST(CAST('1.234' AS Decimal(18, 3)) AS DateTime64(3, 'UTC'))
FORMAT csv;
```

```text
"1970-01-01 00:00:01.234","1970-01-01 00:00:01.234"
```

### Reducing precision

```sql
SELECT CAST(
    CAST('2025-03-05 12:30:00.123456' AS DateTime64(6))
    AS DateTime64(3)
)
FORMAT csv;
```

```text
"2025-03-05 12:30:00.123"
```