Temporal#

Function	Description
DATE	Converts a formatted string date to an actual Date type.
DATE_PART	Extracts a part of a date (or datetime) such as ‘year’, ‘month’, etc.
EXTRACT	Offers the same functionality as `DATE_PART` with slightly different syntax.

DATE#

Converts a formatted string date to an actual Date type; ISO-8601 format is assumed unless a strftime-compatible formatting string is provided as the second parameter.

Example:

df = pl.DataFrame({"str_date": ["1969.10.30", "2024.07.05", "2077.02.28"]})
df.sql("""
  SELECT str_date, DATE(str_date, '%Y.%m.%d') AS date FROM self
""")
# shape: (3, 2)
# ┌────────────┬────────────┐
# │ str_date   ┆ date       │
# │ ---        ┆ ---        │
# │ str        ┆ date       │
# ╞════════════╪════════════╡
# │ 1969.10.30 ┆ 1969-10-30 │
# │ 2024.07.05 ┆ 2024-07-05 │
# │ 2077.02.28 ┆ 2077-02-28 │
# └────────────┴────────────┘

DATE_PART#

Extracts a part of a date (or datetime) such as ‘year’, ‘month’, etc.

Supported parts/fields:

“day”
“dayofweek” | “dow”
“dayofyear” | “doy”
“decade”
“epoch”
“hour”
“isodow”
“isoweek” | “week”
“isoyear”
“microsecond(s)”
“millisecond(s)”
“nanosecond(s)”
“minute”
“month”
“quarter”
“second”
“time”
“year”

Example:

df = pl.DataFrame(
  {
      "dt": [
          date(1969, 12, 31),
          date(2026, 8, 22),
          date(2077, 2, 10),
      ]
  }
)
df.sql("""
  SELECT
    dt,
    DATE_PART(dt, 'year') AS year,
    DATE_PART(dt, 'month') AS month,
    DATE_PART(dt, 'day') AS day
  FROM self
""")

# shape: (3, 4)
# ┌────────────┬──────┬───────┬─────┐
# │ dt         ┆ year ┆ month ┆ day │
# │ ---        ┆ ---  ┆ ---   ┆ --- │
# │ date       ┆ i32  ┆ i8    ┆ i8  │
# ╞════════════╪══════╪═══════╪═════╡
# │ 1969-12-31 ┆ 1969 ┆ 12    ┆ 31  │
# │ 2026-08-22 ┆ 2026 ┆ 8     ┆ 22  │
# │ 2077-02-10 ┆ 2077 ┆ 2     ┆ 10  │
# └────────────┴──────┴───────┴─────┘

EXTRACT#

Extracts a part of a date (or datetime) such as ‘year’, ‘month’, etc.

Supported parts/fields:

“day”
“dayofweek” | “dow”
“dayofyear” | “doy”
“decade”
“epoch”
“hour”
“isodow”
“isoweek” | “week”
“isoyear”
“microsecond(s)”
“millisecond(s)”
“nanosecond(s)”
“minute”
“month”
“quarter”
“second”
“time”
“year”

df = pl.DataFrame(
  {
      "dt": [
          date(1969, 12, 31),
          date(2026, 8, 22),
          date(2077, 2, 10),
      ]
  }
)
df.sql("""
  SELECT
    dt,
    EXTRACT(decade FROM dt) AS decade,
    EXTRACT(year FROM dt) AS year,
    EXTRACT(quarter FROM dt) AS quarter,
  FROM self
""")

# shape: (3, 4)
# ┌────────────┬────────┬──────┬─────────┐
# │ dt         ┆ decade ┆ year ┆ quarter │
# │ ---        ┆ ---    ┆ ---  ┆ ---     │
# │ date       ┆ i32    ┆ i32  ┆ i8      │
# ╞════════════╪════════╪══════╪═════════╡
# │ 1969-12-31 ┆ 196    ┆ 1969 ┆ 4       │
# │ 2026-08-22 ┆ 202    ┆ 2026 ┆ 3       │
# │ 2077-02-10 ┆ 207    ┆ 2077 ┆ 1       │
# └────────────┴────────┴──────┴─────────┘