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

> ## 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.

# last_day

*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) › Names and calendar.* Returns the last day of the month of a date or timestamp, as a `DATE`. Leap years are taken into account.

## Syntax

```
last_day(value)
```

| Argument | Type | Description |
| --- | --- | --- |
| `value` | `DATE` or `TIMESTAMP` (also `TIMESTAMP_NS`, `TIMESTAMP_MS`, `TIMESTAMP_S`) | A day in the month. |

**Returns:** `DATE`, also for a `TIMESTAMP`.

## 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_last_day`. 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 seven 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, row 5 is a leap day, and row 6 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_last_day"'

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 '2024-02-29', TIMESTAMP '2024-02-29 00:00:00', TIME '00:00:00', "
    "CAST('2024-02-29 00:00:00' AS TIMESTAMP_NS)), "
    "(6, 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)), "
    "(7, DATE '2027-01-03', TIMESTAMP '2027-01-03 00:00:00.5', TIME '00:00:00.000001', "
    "CAST('2027-01-03 00:00:00.5' AS TIMESTAMP_NS))")
```

```
[]
[]
[(7,)]
```

## What it does

`last_day` returns the date of the last day of the month that the value falls in. February follows the Gregorian leap-year rule: a year divisible by 4 is a leap year, except a century year that isn't divisible by 400:

| Input | Result |
| --- | --- |
| `DATE &apos;2024-02-10&apos;` | `2024-02-29` |
| `DATE &apos;2023-02-10&apos;` | `2023-02-28` |
| `DATE &apos;2000-02-10&apos;` | `2000-02-29` |
| `DATE &apos;1900-02-10&apos;` | `1900-02-28` |
| `DATE &apos;2026-12-31&apos;` (already the last day) | `2026-12-31` |
| `TIMESTAMP &apos;2026-04-30 23:59:59&apos;` | `2026-04-30`, a `DATE`: the time of day is dropped |

## NULLs and edge cases

| Input | Result |
| --- | --- |
| A NULL value (row 4) | `NULL` |
| An untyped `NULL`: `last_day(NULL)` | `NULL` |
| `DATE &apos;infinity&apos;`, `TIMESTAMP &apos;-infinity&apos;` | `NULL` |
| `DATE &apos;0001-01-01&apos;` | `0001-01-31` |
| `DATE &apos;9999-12-31&apos;` | `9999-12-31` |
| `TIMESTAMP &apos;1969-12-31 23:59:59.999999&apos;` | `1969-12-31` |
| An `INTERVAL` | Error: `No function matches the given name and argument types &apos;last_day(INTERVAL)&apos;` |
| A `TIME` | Error: `No function matches the given name and argument types &apos;last_day(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;last_day(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-last-day#set-up-the-examples):

```
run(f"SELECT id, last_day(ts) FROM {TABLE} WHERE id = 4")
run("SELECT last_day(DATE '2024-02-10'), last_day(DATE '2023-02-10'), last_day(DATE '2000-02-10'), "
    "last_day(DATE '1900-02-10'), last_day(DATE '2026-12-31')")
run("SELECT last_day(TIMESTAMP '2026-04-30 23:59:59'), typeof(last_day(TIMESTAMP '2026-04-30 23:59:59'))")
run("SELECT last_day(NULL), last_day(DATE 'infinity'), last_day(TIMESTAMP '-infinity'), "
    "last_day(DATE '0001-01-01'), last_day(DATE '9999-12-31'), last_day(TIMESTAMP '1969-12-31 23:59:59.999999')")
run("SELECT last_day(INTERVAL 1 MONTH)")
run("SELECT last_day(TIME '13:45:30')")
run("SELECT last_day('2026-03-01')")
run("SELECT last_day(123)")
```

```
[(4, None)]
[(datetime.date(2024, 2, 29), datetime.date(2023, 2, 28), datetime.date(2000, 2, 29), datetime.date(1900, 2, 28), datetime.date(2026, 12, 31))]
[(datetime.date(2026, 4, 30), 'DATE')]
[(None, None, None, datetime.date(1, 1, 31), datetime.date(9999, 12, 31), datetime.date(1969, 12, 31))]
InternalError: Binder Error: No function matches the given name and argument types 'last_day(INTERVAL)'. You might need to add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'last_day(TIME)'. You might need to add explicit type casts.
InternalError: Binder Error: Could not choose a best candidate function for the function call "last_day(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'last_day(INTEGER_LITERAL)'. You might need to add explicit type casts.
```

## Examples

The last day of each event's month:

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

```
[(1, datetime.date(2026, 2, 28), datetime.date(2026, 2, 28), datetime.date(2026, 2, 28)), (2, datetime.date(2026, 3, 1), datetime.date(2026, 3, 31), datetime.date(2026, 3, 31)), (3, datetime.date(2024, 12, 30), datetime.date(2024, 12, 31), datetime.date(2024, 12, 31)), (4, None, None, None), (5, datetime.date(2024, 2, 29), datetime.date(2024, 2, 29), datetime.date(2024, 2, 29)), (6, datetime.date(1969, 12, 31), datetime.date(1969, 12, 31), datetime.date(1969, 12, 31)), (7, datetime.date(2027, 1, 3), datetime.date(2027, 1, 31), datetime.date(2027, 1, 31))]
```

The number of days in each event's month is the day of the month of its last day, with [day](/develop/docs/dev-database-reference-sql-functions-date-time-day):

```
run(f"SELECT id, d, day(last_day(d)) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, datetime.date(2026, 2, 28), 28), (2, datetime.date(2026, 3, 1), 31), (3, datetime.date(2024, 12, 30), 31), (4, None, None), (5, datetime.date(2024, 2, 29), 29), (6, datetime.date(1969, 12, 31), 31), (7, datetime.date(2027, 1, 3), 31)]
```

Keep only the events on the last day of a month:

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

```
[(1, datetime.date(2026, 2, 28)), (5, datetime.date(2024, 2, 29)), (6, datetime.date(1969, 12, 31))]
```

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

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

The plan of the last-day example shows the `FILTER` step above the scan:

```
plan(f"SELECT id, d FROM {TABLE} WHERE last_day(d) = d")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             id            │
│             d             │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│     (last_day(d) = d)     │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             d             │
│             id            │
│                           │
└───────────────────────────┘
```

## Make it faster

- **For one month, filter on a range of the raw column.** To select a month, compare the column with its first day and the first day of the next month, such as `d &gt;= DATE &apos;2026-02-01&apos; AND d &lt; DATE &apos;2026-03-01&apos;`, rather than with `last_day(d)`. The range is pushed down to VAST DataBase, so rows outside it never leave storage. The plan for the range has no `FILTER` step:

```
plan(f"SELECT id, d FROM {TABLE} WHERE d >= DATE '2026-02-01' AND d < DATE '2026-03-01'")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             id            │
│             d             │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             d             │
│             id            │
│                           │
└───────────────────────────┘
```

- **Store a flag if you filter on month ends often.** `last_day(d) = d` must be computed for every row. Compute it when you write the rows and keep it in its own column: `is_month_end = true` is pushed down, `last_day(d) = d` isn't.

## Limitations and errors

- **No time-zone support.** On a `TIMESTAMP WITH TIME ZONE` value, such as `now()`, `last_day` 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` or `INTERVAL`.** Both fail with `No function matches the given name and argument types`.
- **`TIMESTAMP_NS` before 1970.** Row 6's `TIMESTAMP_NS` value `1969-12-31 23:59:59.999999999` gives `1970-01-31`, while the `TIMESTAMP` value `1969-12-31 23:59:59.999999` gives `1969-12-31`. If you need the month of nanosecond values before 1970 that are close to midnight at a month end, check the result or store the value as `TIMESTAMP`.

```
run(f"SELECT id, last_day(tns), last_day(ts) FROM {TABLE} WHERE id = 6")
```

```
[(6, datetime.date(1970, 1, 31), datetime.date(1969, 12, 31))]
```

## Similar functions

| Expression | Returns | Result for `DATE &apos;2024-02-10&apos;` (`last_day` gives `2024-02-29`) |
| --- | --- | --- |
| [date_trunc](/develop/docs/dev-database-reference-sql-functions-date-time-date-trunc) `(&apos;month&apos;, d)` | The first day of the month | `2024-02-01` |
| `date_trunc(&apos;month&apos;, d) + INTERVAL 1 MONTH - INTERVAL 1 DAY` | The last day, as a `TIMESTAMP` at midnight | `2024-02-29 00:00:00` |
| The same, cast to `DATE` | The same as `last_day` | `2024-02-29` |
| [make_date](/develop/docs/dev-database-reference-sql-functions-date-time-make-date) `(2024, 3, 1) - 1` | The day before a date you build | `2024-02-29` |

```
run("SELECT last_day(DATE '2024-02-10'), date_trunc('month', DATE '2024-02-10'), "
    "date_trunc('month', DATE '2024-02-10') + INTERVAL 1 MONTH - INTERVAL 1 DAY, "
    "CAST(date_trunc('month', DATE '2024-02-10') + INTERVAL 1 MONTH - INTERVAL 1 DAY AS DATE), "
    "make_date(2024, 3, 1) - 1")
```

```
[(datetime.date(2024, 2, 29), datetime.date(2024, 2, 1), datetime.datetime(2024, 2, 29, 0, 0), datetime.date(2024, 2, 29), datetime.date(2024, 2, 29))]
```

Clean up:

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

```
[]
[]
```

## See also

- [date_trunc](/develop/docs/dev-database-reference-sql-functions-date-time-date-trunc): the first day of the month, week or year.
- [day](/develop/docs/dev-database-reference-sql-functions-date-time-day) and [month](/develop/docs/dev-database-reference-sql-functions-date-time-month): parts of a date.
- [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.