Python calendar.monthrange() Function

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The Python calendar.monthrange() function returns a tuple containing the first weekday of the month and the number of days in the month.

This function is useful for determining the starting weekday and length of a given month.

Syntax

Following is the syntax of the Python calendar.monthrange() function −

calendar.monthrange(year, month)

Parameters

This function accepts the following parameters −

• year: The year of the month to be checked.
• month: The month (1-12) to be checked.

Return Value

This function returns a tuple (first_weekday, num_days), where −

• first_weekday: An integer (0=Monday, 6=Sunday) representing the first day of the month.
• num_days: The total number of days in the month.

Example: Getting First Weekday and Number of Days

In this example, we get the details for March 2025 using the calendar.monthrange() function −

import calendar

# Get first weekday and number of days in March 2025
first_day, num_days = calendar.monthrange(2025, 3)

print("First weekday:", first_day)
print("Number of days:", num_days)

Following is the output obtained −

First weekday: 5
Number of days: 31

Example: Checking if a Month Starts on a Specific Day

We can check if a month starts on a given weekday as shown in the example below −

import calendar

# Get first weekday for March 2025
first_day, _ = calendar.monthrange(2025, 3)

# Check if it starts on a Monday
if first_day == calendar.MONDAY:
   print("March 2025 starts on a Monday.")
else:
   print("March 2025 does not start on a Monday.")

Following is the output of the above code −

March 2025 does not start on a Monday.

Example: Getting the Last Day of a Month

We can use the monthrange() function to find the last day of a month as follows −

import calendar

# Get number of days in February 2024
_, num_days = calendar.monthrange(2024, 2)

print("Last day of February 2024:", num_days)

We get the output as shown below −

Last day of February 2024: 29

Example: Iterating Over Months in a Year

We can iterate over all months of a year to print their first weekday and number of days −

import calendar

# Iterate through all months of 2025
for month in range(1, 13):
   first_day, num_days = calendar.monthrange(2025, month)
   print(f"Month {month}: First weekday = {first_day}, Days = {num_days}")

The result produced is as shown below −

Month 1: First weekday = 2, Days = 31
Month 2: First weekday = 5, Days = 28
Month 3: First weekday = 5, Days = 31
...
Month 12: First weekday = 1, Days = 31