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

> ## 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.

# month

*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 month of a date or timestamp, from 1 (January) to 12 (December), or the months field of an interval.

## Syntax

```
month(value)
```

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

**Returns:** `BIGINT`.

**Same as:** `date_part('month', value)` and `extract(month FROM value)`; 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_month`. 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`), a timestamp (`ts`), a time of day (`t`) and a timestamp with nanoseconds (`tns`). 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_month"'

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, t TIME, tns TIMESTAMP_NS)")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, DATE '2026-02-28', TIMESTAMP '2026-02-28 23:15:00', TIME '23:15:00', "
    "CAST('2026-02-28 23:15:00.123456789' AS TIMESTAMP_NS)), "
    "(2, DATE '2026-03-01', TIMESTAMP '2026-03-01 08:30:45.123456', TIME '08:30:45.123456', "
    "CAST('2026-03-01 08:30:45.123456' AS TIMESTAMP_NS)), "
    "(3, DATE '2024-12-30', TIMESTAMP '2024-12-30 12:00:00', TIME '12:00:00', "
    "CAST('2024-12-30 12:00:00' AS TIMESTAMP_NS)), "
    "(4, NULL, NULL, NULL, NULL), "
    "(5, DATE '1969-12-31', TIMESTAMP '1969-12-31 23:59:59.999999', TIME '23:59:59.999999', "
    "CAST('1969-12-31 23:59:59.999999999' AS TIMESTAMP_NS))")
```

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

## What it does

`month` returns the month of a date or timestamp as a number: `month(DATE &apos;2024-02-29&apos;)` is `2`. It works on every timestamp precision (`TIMESTAMP`, `TIMESTAMP_NS`, `TIMESTAMP_MS`, `TIMESTAMP_S`). For the month's name, use [monthname](/develop/docs/dev-database-reference-sql-functions-date-time-monthname).

On an `INTERVAL`, `month` returns the months left over after whole years, and doesn't turn days into months:

| Interval | `month` | Why |
| --- | --- | --- |
| `INTERVAL &apos;1 year 2 months 3 days&apos;` | `2` | The months field |
| `INTERVAL &apos;30 months&apos;` | `6` | 30 months is 2 years and 6 months |
| `INTERVAL &apos;-13 months&apos;` | `-1` | Minus 1 year and 1 month |
| `INTERVAL &apos;40 days&apos;` | `0` | Days aren't counted as months |

## 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;` | `12` |
| 44 BC: `CAST(&apos;0044-03-15 (BC)&apos; AS DATE)` | `3` |
| `INTERVAL &apos;-1 year -2 months -3 days -04:05:06.789&apos;` | `-2` |
| `INTERVAL &apos;25 months 40 days 30 hours&apos;` | `1` |
| An untyped `NULL`: `month(NULL)` | Error: `Could not choose a best candidate function for the function call &quot;month(&quot;NULL&quot;)&quot;` |
| A `TIME` | Error: `No function matches the given name and argument types &apos;month(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;month(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-month#set-up-the-examples):

```
run(f"SELECT id, month(ts) FROM {TABLE} WHERE id = 4")
run("SELECT month(DATE 'infinity'), month(TIMESTAMP '-infinity'), month(DATE '0001-01-01'), month(DATE '9999-12-31'), "
    "month(CAST('0044-03-15 (BC)' AS DATE))")
run("SELECT month(INTERVAL '1 year 2 months 3 days'), month(INTERVAL '30 months'), month(INTERVAL '-13 months'), "
    "month(INTERVAL '40 days'), month(INTERVAL '-1 year -2 months -3 days -04:05:06.789'), "
    "month(INTERVAL '25 months 40 days 30 hours')")
run("SELECT month(NULL)")
run("SELECT month(TIME '13:45:30')")
run("SELECT month('2024-02-29')")
run("SELECT month(123)")
```

```
[(4, None)]
[(None, None, 1, 12, 3)]
[(2, 6, -1, 0, -2, 1)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "month("NULL")". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'month(TIME)'. You might need to add explicit type casts.
InternalError: Binder Error: Could not choose a best candidate function for the function call "month(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'month(INTEGER_LITERAL)'. You might need to add explicit type casts.
```

## Examples

The month of each event's date and timestamp, with its name:

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

```
[(1, 2, 2, 'February'), (2, 3, 3, 'March'), (3, 12, 12, 'December'), (4, None, None, None), (5, 12, 12, 'December')]
```

Keep only the events in February of any year:

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

```
[(1,)]
```

## 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 `month()` is always computed by the Query Engine:

- **In the `SELECT` list,** the scan reads the column and the Query Engine computes `month()` for each row it returns.
- **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `month()` 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 month(d) = 2")
```

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

## Make it faster

- **For one month of one year, filter on a range of the raw column.** `ts &gt;= TIMESTAMP &apos;2026-02-01 00:00:00&apos; AND ts &lt; TIMESTAMP &apos;2026-03-01 00:00:00&apos;` is February 2026, and it's pushed down to VAST DataBase, so rows from other months never leave storage. The plan for the range has no `FILTER` step:

```
plan(f"SELECT id FROM {TABLE} WHERE ts >= TIMESTAMP '2026-02-01 00:00:00' AND ts < TIMESTAMP '2026-03-01 00:00:00'")
```

```
┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
```

- **Store the month if you filter on it across years.** `month(d) = 2` for every year has no single range. Compute the month when you write the rows and keep it in its own column: `event_month = 2` is pushed down, `month(d) = 2` isn't.
- **Don't write the range with `date_trunc`.** `date_trunc(&apos;month&apos;, ts) = TIMESTAMP &apos;2026-02-01 00:00:00&apos;` is a function of the column too, and runs in the Query Engine; see [date_trunc](/develop/docs/dev-database-reference-sql-functions-date-time-date-trunc).

## Limitations and errors

- **No time-zone support.** On a `TIMESTAMP WITH TIME ZONE` value, such as `now()`, `month` 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).
- **Not for `TIME`.** `month(TIME ...)` fails with `No function matches the given name and argument types &apos;month(TIME)&apos;`.
- **`TIMESTAMP_NS` just before 1970.** Row 5's `tns`, `1969-12-31 23:59:59.999999999`, gives `1`, not `12`. Store such values as `TIMESTAMP` if you need their month.

```
run(f"SELECT id, month(tns), month(ts) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, 2, 2), (2, 3, 3), (3, 12, 12), (4, None, None), (5, 1, 12)]
```

## Similar functions

| Function | Returns | Result for `DATE &apos;2024-02-29&apos;` (`month` gives `2`) |
| --- | --- | --- |
| [monthname](/develop/docs/dev-database-reference-sql-functions-date-time-monthname) | The month's English name | `&apos;February&apos;` |
| [date_trunc](/develop/docs/dev-database-reference-sql-functions-date-time-date-trunc) with `&apos;month&apos;` | The first day of the month, as a `DATE` | `2024-02-01` |
| [last_day](/develop/docs/dev-database-reference-sql-functions-date-time-last-day) | The last day of the month | `2024-02-29` |
| [strftime](/develop/docs/dev-database-reference-sql-functions-date-time-strftime) with `&apos;%m&apos;` | The month as two-digit text | `&apos;02&apos;` |
| [quarter](/develop/docs/dev-database-reference-sql-functions-date-time-quarter) | The quarter, 1 to 4 | `1` |

```
run("SELECT month(DATE '2024-02-29'), monthname(DATE '2024-02-29'), date_trunc('month', DATE '2024-02-29'), "
    "last_day(DATE '2024-02-29'), strftime(DATE '2024-02-29', '%m'), quarter(DATE '2024-02-29')")
```

```
[(2, 'February', datetime.date(2024, 2, 1), datetime.date(2024, 2, 29), '02', 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.