relationalai.std.dates.day()

day(date: date|datetime|Producer, tz: str|Producer = "UTC") -> Expression

Extracts the day component from a date or UTC datetime value. If tz is specified, then date is converted from UTC to the specified timezone before extracting the day. tz is ignored if date is a Python date or datetime object. If any of the arguments are Producer objects, then day() also acts as a filter and removes invalid values from the producer. Must be called in a rule or query context.

Parameters

Name	Type	Description
date	Producer or Python date or datetime object	The date or datetime value from which to extract the day.
tz	Producer or Python str object	Optional timezone string (e.g., "America/New_York"), offset string (e.g., "+0600"), or Python tzinfo object. Refer to the timezone database for a list of valid timezone identifiers. Ignored if date is a Python date or datetime object. (Default: "UTC").

Returns

An Expression object.

Raises

TypeError if the date parameter is not a Producer object or Python date or datetime object.

Example

Use day() to extract the day component from date and datetime values:

import relationalai as rai
from relationalai.std import alias, dates


# =====
# SETUP
# =====

model = rai.Model("MyModel")
Event = model.Type("Event")

with model.rule():
    Event.add(id=1).set(time=dates.datetime(2021, 1, 1, 1, 30))
    Event.add(id=2).set(time="invalid")


# =======
# EXAMPLE
# =======

with model.rule():
    event = Event()
    # day() filters out any events with invalid time values, so the
    # following only sets the day property for Event 1.
    event.set(day=dates.day(event.time))
    # Since Event 2 is filtered out above, the following only sets the
    # has_valid_time property for Event 1.
    event.set(has_valid_time=True)

with model.query() as select:
    event = Event()
    response = select(event.id, event.time, event.day, event.has_valid_time)

print(response.results)
#    id                 time  month has_valid_time
# 0   1  2021-01-01 01:30:00    1.0           True
# 1   2              invalid    NaN            NaN

If the date parameter is a datetime and the tz parameter is specified, the datetime is converted from UTC to the specified timezone before computing the weekday:

with model.query() as select:
    event = Event()
    day1 = dates.day(event.time, tz="America/New_York")
    day2 = dates.day(event.time, tz="+0600")
    response = select(event.id, event.time, alias(day1, "day1"), alias(day2, "day2"))

print(response.results)
#
with model.query() as select:
    event = Event()
    month1 = dates.month(event.time, tz="America/New_York")
    month2 = dates.month(event.time, tz="+0600")
    response = select(event.id, event.time, alias(month1, "month1"), alias(month2, "month2"))

print(response.results)
#    id                time  month1  month2
# 0   1 2021-01-01 01:30:00      12       1

See Also

• year()
• month()
• hour()
• minute()
• second()