--- title: "era" slug: "dev-database-reference-sql-functions-date-time-era" updated: 2026-10-30T18:19:01Z published: 2026-10-30T18:19:01Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-date-time-era" --- > ## 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. # era *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 era of a date or timestamp: `1` for year 1 and later (AD, or CE), `0` for the years before it (BC, or BCE). ## Syntax ``` era(value) ``` | Argument | Type | Description | | --- | --- | --- | | `value` | `DATE` or `TIMESTAMP` (also `TIMESTAMP_NS`, `TIMESTAMP_MS`, `TIMESTAMP_S`) | The value to take the era of. | **Returns:** `BIGINT`. **Same as:** `date_part('era', value)` and `extract(era 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_era`. 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 four events. Each has a date (`d`) and a timestamp (`ts`). Row 2 is the first day of year 1, row 3 the last day of year 9999, and row 4 has no values: ``` 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_era"' 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, "") 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 '0001-01-01', TIMESTAMP '0001-01-01 00:00:00'), " "(3, DATE '9999-12-31', TIMESTAMP '9999-12-31 23:59:59'), " "(4, NULL, NULL)") ``` ``` [] [] [(4,)] ``` ## What it does `era` returns `1` for a date or timestamp in year 1 or later, and `0` for one before year 1: `DATE '0001-01-01'` gives `1`, and `CAST('0001-01-01 (BC)' AS DATE)` (1 BC) gives `0`. [year](/develop/docs/dev-database-reference-sql-functions-date-time-year) counts the years before year 1 down from 0, so 44 BC is year `-43`, era `0`. Use `era` to label or separate BC dates; for every date after year 1 it's `1`. It works on every timestamp precision. `era` has no meaning for a time of day or an interval: a `TIME` fails to bind, and an `INTERVAL` fails with `interval units "era" not recognized`. ## NULLs and edge cases | Input | Result | | --- | --- | | A NULL value (row 4) | `NULL` | | `DATE 'infinity'`, `TIMESTAMP '-infinity'` | `NULL` | | `DATE '0001-01-01'` | `1` | | `DATE '9999-12-31'` | `1` | | 1 BC: `CAST('0001-01-01 (BC)' AS DATE)` | `0` | | 44 BC: `CAST('0044-03-15 (BC)' AS DATE)` | `0` | | An untyped `NULL`: `era(NULL)` | Error: `Could not choose a best candidate function for the function call "era("NULL")"` | | An `INTERVAL` | Error: `interval units "era" not recognized` | | A `TIME` | Error: `No function matches the given name and argument types 'era(TIME)'` | | 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 `'era(INTEGER_LITERAL)'` | 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-era#set-up-the-examples): ``` run(f"SELECT id, era(d), era(ts) FROM {TABLE} WHERE id = 4") run("SELECT era(DATE 'infinity'), era(TIMESTAMP '-infinity'), era(DATE '0001-01-01'), era(DATE '9999-12-31'), " "era(CAST('0001-01-01 (BC)' AS DATE)), era(CAST('0044-03-15 (BC)' AS DATE))") run("SELECT era(NULL)") run("SELECT era(INTERVAL 1 DAY)") run("SELECT era(TIME '13:45:30')") run("SELECT era('2024-02-29')") run("SELECT era(123)") ``` ``` [(4, None, None)] [(None, None, 1, 1, 0, 0)] InternalError: Binder Error: Could not choose a best candidate function for the function call "era("NULL")". In order to select one, please add explicit type casts. OSError: interval units "era" not recognized InternalError: Binder Error: No function matches the given name and argument types 'era(TIME)'. You might need to add explicit type casts. InternalError: Binder Error: Could not choose a best candidate function for the function call "era(STRING_LITERAL)". In order to select one, please add explicit type casts. InternalError: Binder Error: No function matches the given name and argument types 'era(INTEGER_LITERAL)'. You might need to add explicit type casts. ``` ## Examples The era and year of each event: ``` run(f"SELECT id, era(d), year(d), era(ts) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 1, 2026, 1), (2, 1, 1, 1), (3, 1, 9999, 1), (4, None, None, None)] ``` Label a date with its era. A BC year is `1 - year(d)`: 44 BC is year `-43`: ``` run("SELECT CASE WHEN era(CAST('0044-03-15 (BC)' AS DATE)) = 0 " "THEN CAST(1 - year(CAST('0044-03-15 (BC)' AS DATE)) AS VARCHAR) || ' BC' " "ELSE CAST(year(CAST('0044-03-15 (BC)' AS DATE)) AS VARCHAR) || ' AD' END") ``` ``` [('44 BC',)] ``` Keep only the events in the current era. This works, but [Make it faster](/develop/docs/dev-database-reference-sql-functions-date-time-era#make-it-faster) has a faster way to write it: ``` run(f"SELECT id FROM {TABLE} WHERE era(d) = 1 ORDER BY id LIMIT 10") ``` ``` [(1,), (2,), (3,)] ``` ## 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 `era()` is always computed by the Query Engine: - **In the `SELECT` list,** the scan reads the column and the Query Engine computes `era()` for each row it returns. - **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `era()` 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 era(d) = 1") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ (era(d) = 1) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ d │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Compare the raw column with the first day of year 1, not `era()`.** `d >= DATE '0001-01-01'` returns the same rows as `era(d) = 1`, and `d < DATE '0001-01-01'` the same as `era(d) = 0`. A comparison of the column with a constant is pushed down to VAST DataBase, so the plan has no `FILTER` step: ``` run(f"SELECT id FROM {TABLE} WHERE d >= DATE '0001-01-01' ORDER BY id LIMIT 10") plan(f"SELECT id FROM {TABLE} WHERE d >= DATE '0001-01-01'") ``` ``` [(1,), (2,), (3,)] ┌───────────────────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ Projections: id │ │ │ └───────────────────────────┘ ``` ## Limitations and errors - **Dates and timestamps only.** `era` of an `INTERVAL` fails with `interval units "era" not recognized`, although the error for a wrong argument lists `era(INTERVAL)`. `era` of a `TIME` fails with `No function matches the given name and argument types 'era(TIME)'`, and `extract(era FROM TIME ...)` with `"time" units "era" not recognized`. - **No time-zone support.** On a `TIMESTAMP WITH TIME ZONE` value, such as `now()`, `era` 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). - **No `date_trunc('era', ...)`.** It fails with `Specifier type not implemented for DATETRUNC statistics`. Compare with `DATE '0001-01-01'` instead. ``` run("SELECT extract(era FROM TIME '13:45:30')") run("SELECT date_trunc('era', DATE '2024-02-29')") ``` ``` OSError: "time" units "era" not recognized InternalError: Not implemented Error: Specifier type not implemented for DATETRUNC statistics ``` ## Similar functions | Function | Returns | Result for 44 BC, `CAST('0044-03-15 (BC)' AS DATE)` (`era` gives `0`) | | --- | --- | --- | | [year](/develop/docs/dev-database-reference-sql-functions-date-time-year) | The year, counting down from 0 before year 1 | `-43` | | [century](/develop/docs/dev-database-reference-sql-functions-date-time-century) | The century, negative before year 1 | `-1` | | [millennium](/develop/docs/dev-database-reference-sql-functions-date-time-millennium) | The millennium, negative before year 1 | `-1` | | [decade](/develop/docs/dev-database-reference-sql-functions-date-time-decade) | The year divided by 10 | `-4` | ``` run("SELECT era(CAST('0044-03-15 (BC)' AS DATE)), year(CAST('0044-03-15 (BC)' AS DATE)), " "century(CAST('0044-03-15 (BC)' AS DATE)), millennium(CAST('0044-03-15 (BC)' AS DATE)), " "decade(CAST('0044-03-15 (BC)' AS DATE))") ``` ``` [(0, -43, -1, -1, -4)] ``` 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.