---
title: "millennium"
slug: "dev-database-reference-sql-functions-date-time-millennium"
updated: 2026-10-30T18:19:01Z
published: 2026-10-30T18:19:01Z
canonical: "docs.vastdata.com/dev-database-reference-sql-functions-date-time-millennium"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# millennium

*Applies to VAST Cluster 5.5.*

*[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Date and time functions](/develop/docs/dev-database-reference-sql-functions-date-time) › Parts of a date or time.* Returns the millennium of a date or timestamp, counted from year 1: the years 2001 to 3000 are millennium `3`. On an interval, it returns the whole millennia in its years.

## Syntax

```
millennium(value)
```

| Argument | Type | Description |
| --- | --- | --- |
| `value` | `DATE`, `TIMESTAMP` (also `TIMESTAMP_NS`, `TIMESTAMP_MS`, `TIMESTAMP_S`) or `INTERVAL` | The value to take the millennium of. |

**Returns:** `BIGINT`.

**Same as:** `date_part('millennium', value)` and `extract(millennium FROM value)`; the part also has the names `mil`, `millennia` and `millenniums`. See [date_part](/develop/docs/dev-database-reference-sql-functions-date-time-date-part).

## Set up the examples

The examples connect with the ADBC driver, as in [VAST Query Engine (ADBC)](/develop/docs/dev-database-integrations-adbc), and work in a schema called `docs_sql_fn_date_time_millennium`. Set `QE_ENDPOINT`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY` and `VASTDB_BUCKET` ([SQL reference](/develop/docs/dev-database-reference-sql-index#example-connect-and-use-a-transaction)), and run the blocks in order in one Python session. Below each block is the output you should see.

This block connects, defines the `run()` and `plan()` helpers, and creates a table of five events. Each has a date (`d`) and a timestamp (`ts`). Rows 2 and 3 are either side of the start of the 3rd millennium, row 4 has no values, and row 5 is the last moment of 1969:

```
import os
import re

import adbc_driver_manager
import adbc_driver_manager.dbapi as dbapi
import adbc_driver_vastdb

BUCKET = os.environ["VASTDB_BUCKET"]
SCHEMA = f'"{BUCKET}/docs_sql_fn_date_time_millennium"'

conn = dbapi.connect(
    driver=adbc_driver_vastdb.get_driver_path(),
    db_kwargs={
        "vast.db.endpoint": os.environ["QE_ENDPOINT"],
        "vast.db.access_key": os.environ["AWS_ACCESS_KEY_ID"],
        "vast.db.secret_key": os.environ["AWS_SECRET_ACCESS_KEY"],
    },
    autocommit=True,
)

def server_message(e):
    """The server's message in a driver error, without the request ID or the echoed statement."""
    text = re.sub(r"\[req=0x[0-9a-f]+\]: ", "", str(e))
    found = (re.search(r'message: "(.*?)", request_id', text, re.S)
             or re.search(r"description: (.*)\)", text, re.S))
    message = found.group(1) if found else text.strip().splitlines()[-1]
    message = re.sub(r"^Plan query: '.*?' failed with: ", "", message, flags=re.S)
    message = re.split(r"\\n|\n", message)[0].replace('\\"', '"')
    return message.replace(BUCKET, "<bucket>")

def run(sql):
    """Run one statement. Print the rows it returns, or the error."""
    try:
        with conn.cursor() as cur:
            cur.execute(sql)
            rows = cur.fetchall() if cur.description else []
    except (adbc_driver_manager.Error, OSError) as e:
        print(f"{type(e).__name__}: {server_message(e)}")
    else:
        print(rows)

def plan(sql):
    """Print the plan without its ~N Rows lines: the table's row count, which can still be 0 just after an insert."""
    with conn.cursor() as cur:
        cur.execute("EXPLAIN " + sql)
        steps = cur.fetchall()[0][1]
    print("\n".join(line for line in steps.splitlines() if "Rows" not in line))

TABLE = f"{SCHEMA}.events"
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, d DATE, ts TIMESTAMP)")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, DATE '2026-02-28', TIMESTAMP '2026-02-28 23:15:00'), "
    "(2, DATE '2000-12-31', TIMESTAMP '2000-12-31 12:00:00'), "
    "(3, DATE '2001-01-01', TIMESTAMP '2001-01-01 00:00:00'), "
    "(4, NULL, NULL), "
    "(5, DATE '1969-12-31', TIMESTAMP '1969-12-31 23:59:59.999999')")
```

```
[]
[]
[(5,)]
```

## What it does

`millennium` counts millennia from year 1: the 1st millennium is years 1 to 1000, the 2nd is 1001 to 2000, and the 3rd is 2001 to 3000. So `millennium(DATE &apos;2000-12-31&apos;)` is `2` and `millennium(DATE &apos;2001-01-01&apos;)` is `3`. The last date a `DATE` can hold, 9999-12-31, is in millennium `10`. It works on every timestamp precision.

Years before year 1 are in millennium `-1`: both 44 BC and 1 BC give `-1`.

On an `INTERVAL`, `millennium` returns the whole millennia in its years: `millennium(INTERVAL &apos;2500 years&apos;)` is `2`. An interval of less than 1000 years gives `0`.

## NULLs and edge cases

| Input | Result |
| --- | --- |
| A NULL value (row 4) | `NULL` |
| `DATE &apos;infinity&apos;`, `TIMESTAMP &apos;-infinity&apos;` | `NULL` |
| `DATE &apos;0001-01-01&apos;` | `1` |
| `DATE &apos;9999-12-31&apos;` | `10` |
| 44 BC: `CAST(&apos;0044-03-15 (BC)&apos; AS DATE)` | `-1` |
| 1 BC: `CAST(&apos;0001-01-01 (BC)&apos; AS DATE)` | `-1` |
| `INTERVAL &apos;2500 years&apos;` | `2` |
| `INTERVAL &apos;25 months 40 days 30 hours&apos;` | `0` |
| An untyped `NULL`: `millennium(NULL)` | Error: `Could not choose a best candidate function for the function call &quot;millennium(&quot;NULL&quot;)&quot;` |
| A `TIME` | Error: `No function matches the given name and argument types &apos;millennium(TIME)&apos;` |
| A string | Error: `Could not choose a best candidate function`; cast it to `DATE` first |
| A number, boolean, `BLOB` or list | Error: `No function matches the given name and argument types`, for example `&apos;millennium(INTEGER_LITERAL)&apos;` |

The same cases, as the cluster returns them. They use the table and helpers from [Set up the examples](/develop/docs/dev-database-reference-sql-functions-date-time-millennium#set-up-the-examples):

```
run(f"SELECT id, millennium(d), millennium(ts) FROM {TABLE} WHERE id = 4")
run("SELECT millennium(DATE 'infinity'), millennium(TIMESTAMP '-infinity'), millennium(DATE '0001-01-01'), "
    "millennium(DATE '9999-12-31'), millennium(CAST('0044-03-15 (BC)' AS DATE)), "
    "millennium(CAST('0001-01-01 (BC)' AS DATE))")
run("SELECT millennium(INTERVAL '2500 years'), millennium(INTERVAL '25 months 40 days 30 hours')")
run("SELECT millennium(NULL)")
run("SELECT millennium(TIME '13:45:30')")
run("SELECT millennium('2024-02-29')")
run("SELECT millennium(123)")
```

```
[(4, None, None)]
[(None, None, 1, 10, -1, -1)]
[(2, 0)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "millennium("NULL")". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'millennium(TIME)'. You might need to add explicit type casts.
InternalError: Binder Error: Could not choose a best candidate function for the function call "millennium(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'millennium(INTEGER_LITERAL)'. You might need to add explicit type casts.
```

## Examples

The millennium of each event's date and timestamp, next to its year. Rows 2 and 3 are a day apart but in different millennia:

```
run(f"SELECT id, year(d), millennium(d), millennium(ts) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, 2026, 3, 3), (2, 2000, 2, 2), (3, 2001, 3, 3), (4, None, None, None), (5, 1969, 2, 2)]
```

Keep only the events from the 2nd millennium. This works, but [Make it faster](/develop/docs/dev-database-reference-sql-functions-date-time-millennium#make-it-faster) has a faster way to write it:

```
run(f"SELECT id FROM {TABLE} WHERE millennium(d) = 2 ORDER BY id LIMIT 10")
```

```
[(2,), (5,)]
```

## How it runs in VAST

The Query Engine runs on the cluster's CNodes, and a query on a table starts with a scan in VAST DataBase (`VAST_SCAN`). VAST DataBase can evaluate a comparison of a column with a constant, but not a function of a column, so `millennium()` is always computed by the Query Engine:

- **In the `SELECT` list,** the scan reads the column and the Query Engine computes `millennium()` for each row it returns.
- **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `millennium()` and keeps the rows that match. No rows are skipped in storage.

The plan of the `WHERE` example shows the `FILTER` step above the scan:

```
plan(f"SELECT id FROM {TABLE} WHERE millennium(d) = 2")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│   ("millennium"(d) = 2)   │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             d             │
│             id            │
│                           │
└───────────────────────────┘
```

## Make it faster

- **Filter on a range of the raw column, not on `millennium()`.** `d &gt;= DATE &apos;1001-01-01&apos; AND d &lt; DATE &apos;2001-01-01&apos;` returns the same rows as `millennium(d) = 2`, and it's pushed down to VAST DataBase, so rows from other millennia never leave storage. The plan for the range has no `FILTER` step:

```
run(f"SELECT id FROM {TABLE} WHERE d >= DATE '1001-01-01' AND d < DATE '2001-01-01' ORDER BY id LIMIT 10")
plan(f"SELECT id FROM {TABLE} WHERE d >= DATE '1001-01-01' AND d < DATE '2001-01-01'")
```

```
[(2,), (5,)]
┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
```

## Limitations and errors

- **Dates and timestamps only, not `TIME`.** A time of day has no year, so `millennium(TIME ...)` fails with `No function matches the given name and argument types &apos;millennium(TIME)&apos;`.
- **No time-zone support.** On a `TIMESTAMP WITH TIME ZONE` value, such as `now()`, `millennium` fails with an `Extension Autoloading Error`. Cast the value to `TIMESTAMP` first; see [time zones](/develop/docs/dev-database-reference-sql-functions-date-time-time-zones).
- **`date_trunc(&apos;millennium&apos;, ...)` uses other boundaries.** It returns the first day of a year that's a multiple of 1000: `date_trunc(&apos;millennium&apos;, DATE &apos;2026-03-01&apos;)` is `2000-01-01`, a day that `millennium()` puts in the 2nd millennium. To get the first day of the millennium that `millennium()` reports, use `make_date((millennium(d) - 1) * 1000 + 1, 1, 1)`.

```
run("SELECT millennium(DATE '2026-03-01'), date_trunc('millennium', DATE '2026-03-01'), "
    "millennium(date_trunc('millennium', DATE '2026-03-01')), "
    "make_date((millennium(DATE '2026-03-01') - 1) * 1000 + 1, 1, 1)")
```

```
[(3, datetime.date(2000, 1, 1), 2, datetime.date(2001, 1, 1))]
```

## Similar functions

| Function | Returns | Result for `DATE &apos;2000-12-31&apos;` (`millennium` gives `2`) |
| --- | --- | --- |
| [year](/develop/docs/dev-database-reference-sql-functions-date-time-year) | The calendar year | `2000` |
| [decade](/develop/docs/dev-database-reference-sql-functions-date-time-decade) | The year divided by 10 | `200` |
| [century](/develop/docs/dev-database-reference-sql-functions-date-time-century) | The century, counted from year 1 | `20` |
| [date_trunc](/develop/docs/dev-database-reference-sql-functions-date-time-date-trunc) with `&apos;millennium&apos;` | The first day of a year that's a multiple of 1000, as a `DATE` | `2000-01-01` |

```
run("SELECT millennium(DATE '2000-12-31'), year(DATE '2000-12-31'), decade(DATE '2000-12-31'), "
    "century(DATE '2000-12-31'), date_trunc('millennium', DATE '2000-12-31')")
```

```
[(2, 2000, 200, 20, datetime.date(2000, 1, 1))]
```

Clean up:

```
run(f"DROP TABLE IF EXISTS {TABLE}")
run(f"DROP SCHEMA IF EXISTS {SCHEMA}")
conn.close()
```

```
[]
[]
```

## See also

- [date_part](/develop/docs/dev-database-reference-sql-functions-date-time-date-part): any part of a value, by name.
- [Date and time functions](/develop/docs/dev-database-reference-sql-functions-date-time): all the date and time functions.
- [Where filters run](/develop/docs/dev-database-reference-sql-select#where-filters-run) and [pushdowns](/develop/docs/dev-database-reference-pushdowns).
- [EXPLAIN](/develop/docs/dev-database-reference-sql-explain): how to read a plan.