date.isocalendar() to get ISO year, ISO week number, ISO weekday from date object

isocalendar() : to get ISO year, ISO week number, ISO weekday

Today's isocalendar()

from datetime import date

dt = date.today()
print(dt.isocalendar())

Output ( will change based on current date )

(2019, 38, 2)

The date.isocalendar() function returns a tuple with the ISO year, ISO week number, and ISO weekday for a given date. This is especially useful for analyzing data by week or aligning with ISO standards in project timelines.

Using date and time object

from datetime import date

dt = date(2019, 12, 31)
print(dt.isocalendar())

Output

datetime.IsoCalendarDate(year=2020, week=1, weekday=2)

Syntax

date_object.isocalendar()

Example 2: ISO Calendar for a Specific Date

Calculate the ISO week and weekday for a specified date.

from datetime import date

specific_date = date(2022, 12, 31)
print(specific_date.isocalendar())

Output:

datetime.IsoCalendarDate(year=2022, week=52, weekday=6)

Example 3: Using ISO Week in a Loop

Iterate over a range of dates and print the ISO week for each.

from datetime import date, timedelta

start_date = date(2024, 12, 25)
for i in range(7):
    current_date = start_date + timedelta(days=i)
    iso_year, iso_week, iso_weekday = current_date.isocalendar()
    print(f"Date: {current_date}, ISO Week: {iso_week}")

Output

Date: 2024-12-25, ISO Week: 52
Date: 2024-12-26, ISO Week: 52
Date: 2024-12-27, ISO Week: 52
Date: 2024-12-28, ISO Week: 52
Date: 2024-12-29, ISO Week: 52
Date: 2024-12-30, ISO Week: 1 
Date: 2024-12-31, ISO Week: 1

Example 4: Creating a Week-Based Report

This example demonstrates creating a weekly summary using ISO weeks.

from datetime import date, timedelta

dates = [date(2022, 12, 24), 
          date(2022, 12, 25), 
          date(2023, 1, 1)]

week_summary = {}

for d in dates:
    iso_week = d.isocalendar()[1]
    week_summary[iso_week] = week_summary.get(iso_week, 0) + 1

print("Weekly summary:", week_summary)

Output:

Weekly summary: {51: 2, 52: 1}

Applications of isocalendar()

Weekly Reports: Track data by ISO week for consistent reporting.
Project Management: Align project milestones with ISO-standard weeks.
Fiscal Year Calculations: Use ISO year and week for fiscal or academic reporting.

All Date Objects

String Functions Math functions Python- Tutorials

Subhendu Mohapatra

Author

🎥 Join me live on YouTube

Passionate about coding and teaching, I publish practical tutorials on PHP, Python, JavaScript, SQL, and web development. My goal is to make learning simple, engaging, and project‑oriented with real examples and source code.

Subscribe to our YouTube Channel here

isocalendar(): Extract ISO Year, Week Number, and Weekday