julian

Applies to VAST Cluster 5.5.

Functions › Date and time functions › Names and calendar. Returns the Julian day number of a date, as a DOUBLE. For a timestamp, the time of day is added as a fraction of a day.

Syntax

julian(value)

Returns: DOUBLE.

Same as: date_part('julian', value) and extract(julian FROM value); see date_part.

Set up the examples

The examples connect with the ADBC driver, as in VAST Query Engine (ADBC), and work in a schema called docs_sql_fn_date_time_julian. Set QE_ENDPOINT, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY and VASTDB_BUCKET (SQL reference), 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_julian"'

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

julian counts days from day 0, 24 November 4714 BC: julian(DATE '2000-01-01') is 2451545.0, and julian(DATE '1970-01-01') is 2440588.0.

On a DATE, the result is a whole number. On a timestamp, the time of day is added as a fraction of a day that starts at midnight: julian(TIMESTAMP '1970-01-01 12:00:00') is 2440588.5. This is half a day more than the astronomical Julian date, which starts each day at noon: epoch(v) / 86400 + 2440587.5 gives that value.

The result is a DOUBLE, so the fraction isn't exact to the microsecond: row 5's timestamp, one microsecond before 1970, gives 2440588.0. Use epoch_us when you need exact microseconds.

NULLs and edge cases

The same cases, as the cluster returns them. They use the table and helpers from Set up the examples:

run(f"SELECT id, julian(ts) FROM {TABLE} WHERE id = 4")
run("SELECT julian(NULL), julian(DATE 'infinity'), julian(TIMESTAMP '-infinity')")
run("SELECT julian(DATE '0001-01-01'), julian(DATE '9999-12-31'), julian(CAST('0044-03-15 (BC)' AS DATE)), "
    "julian(CAST('4714-11-24 (BC)' AS DATE)), julian(TIMESTAMP '1970-01-01 12:00:00')")
run("SELECT julian(TIME '13:45:30')")
run("SELECT julian(INTERVAL '1 day')")
run("SELECT julian('2024-02-29')")
run("SELECT julian(123)")

[(4, None)]
[(None, None, None)]
[(1721426.0, 5373484.0, 1705428.0, 0.0, 2440588.5)]
InternalError: Binder Error: No function matches the given name and argument types 'julian(TIME)'. You might need to add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'julian(INTERVAL)'. You might need to add explicit type casts.
InternalError: Binder Error: Could not choose a best candidate function for the function call "julian(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'julian(INTEGER_LITERAL)'. You might need to add explicit type casts.

Examples

The Julian day of each event's date and timestamp:

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

[(1, 2461100.0, 2461100.96875), (2, 2461101.0, 2461101.354688929), (3, 2460675.0, 2460675.5), (4, None, None), (5, 2440587.0, 2440588.0)]

The number of days between two dates is the difference of their Julian days:

run("SELECT julian(DATE '2026-03-01') - julian(DATE '2024-02-29')")

[(731.0,)]

Keep only the events after Julian day 2461000 (20 November 2025). This works, but Make it faster has a faster way to write it:

run(f"SELECT id FROM {TABLE} WHERE julian(d) > 2461000 ORDER BY id LIMIT 10")

[(1,), (2,)]

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 julian() is always computed by the Query Engine:

• In the SELECT list, the scan reads the column and the Query Engine computes julian() for each row it returns.
• In WHERE, the scan sends the column for every row, and a FILTER step in the Query Engine computes julian() 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 julian(d) > 2461000")

┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│  (julian(d) > 2461000.0)  │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             d             │
│             id            │
│                           │
└───────────────────────────┘

Make it faster

• Compare the raw column with a date, not julian() with a number. d > DATE '2025-11-20' returns the same rows as julian(d) > 2461000, and it's pushed down to VAST DataBase, so rows that don't match never leave storage. The plan has no FILTER step:

plan(f"SELECT id FROM {TABLE} WHERE d > DATE '2025-11-20'")
run(f"SELECT id FROM {TABLE} WHERE d > DATE '2025-11-20' ORDER BY id LIMIT 10")

┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
[(1,), (2,)]

• Use julian() in the SELECT list, where it doesn't stop a filter from being pushed down.

Limitations and errors

• No time-zone support. On a TIMESTAMP WITH TIME ZONE value, such as now(), julian fails with an Extension Autoloading Error. Cast the value to TIMESTAMP first: julian(CAST(now() AS TIMESTAMP)). See time zones.
• Dates and timestamps only. A TIME or an INTERVAL has no day number and fails with No function matches the given name and argument types.
• One argument. julian(ts, ts) fails with No function matches the given name and argument types 'julian(TIMESTAMP, TIMESTAMP)'.

run(f"SELECT julian(ts, ts) FROM {TABLE} LIMIT 1")

InternalError: Binder Error: No function matches the given name and argument types 'julian(TIMESTAMP, TIMESTAMP)'. You might need to add explicit type casts.

Similar functions

run("SELECT julian(DATE '2024-02-29'), date_part('julian', DATE '2024-02-29'), extract(julian FROM DATE '2024-02-29'), "
    "epoch(DATE '2024-02-29') / 86400 + 2440588, dayofyear(DATE '2024-02-29')")

[(2460370.0, 2460370.0, 2460370.0, 2460370.0, 60)]

Clean up:

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

[]
[]

See also

• date_part: any part of a value, by name.
• Date and time functions: all the date and time functions.
• Where filters run and pushdowns.
• EXPLAIN: how to read a plan.