Python Get Last Day of Month

In this Python lesson, you’ll learn how to find the last day (last date) of a month from a given date. Also, we will cover how to get the last day of next month and the previous month.

Also, see Python Get First Day Of Month.

How To Find The Last Day Of The Month In Python

Example: Get The Last Day Of The Month

# Get the last day of the month from a given date
import calendar
from datetime import datetime

input_dt = datetime(2022, 9, 13)
print("The original date is:", input_dt.date())

# monthrange() to gets the date range
# year = 2022, month = 9
res = calendar.monthrange(input_dt.year, input_dt.month)
day = res[1]
print(f"Last date of month is: {input_dt.year}-{input_dt.month}-{day}")

# note:
# res [0]  = weekday of first day (between 0-6 ~ Mon-Sun))
# res [1] = last day of the month

Output:

The original date is: 2022-09-13
Last date of month is: 2022-9-30

Get The Last Day Of The Month Using replace() and timedelta()

If you don’t want to import the calendar module just for this use case, you can use the combination of replace() and timedelta() method of a datetime module.

• datetime.replace(): This method replaces the DateTime object’s contents with the given parameters. This method has various parameters, but here we will use the day parameter because we want to replace the day number of a datetime object with the last day of the month.
• timedelta(): A timedelta represents a duration which is the difference between two dates, time, or datetime instances, to the microsecond resolution. We can use the timedelta to add or subtract weeks, days, hours, minutes, seconds, microseconds, and milliseconds from a given DateTime.

Now, let’s see the steps to achieve the same.

• First, import the datetime and timedelta class from a datetime module.
• Next, use the day parameter of a timedelta class to replace the date’s day number with 28 (each month contains at least 28 days).
• Next, use the timedelta class to add four days to the new date. By doing this, you will get the next month.
• Now, subtract the number of the current day from the new date to get the last day of a month. (It brings us back to the original month).

Example: Get The Last Day Of The Month Using replace() and timedelta()

from datetime import datetime, timedelta

input_dt = datetime(2022, 9, 13)
print("The original date is:", input_dt.date())

next_month = input_dt.replace(day=28) + timedelta(days=4)
res = next_month - timedelta(days=next_month.day)
print(f"Last date of month is:", res.date())

Output:

The original date is: 2022-09-13
Last date of month is: 2022-09-30

Also, see Python Get First Day Of Month.

Get The Last Day Of The Month Using dateutil

Also, we can use the third-party library dateutil to get the last day of a month.

• Use pip Install python-dateutil to install it.
• Next, just add 31 days to your date using the dateutil.relativedelta(day=31) to get the last day of the month.

Example:

from datetime import datetime
from dateutil.relativedelta import relativedelta

input_dt = datetime(2202, 9, 13)
print("The original date is:", input_dt.date())

# add 31 days to the input datetime
res = input_dt + relativedelta(day=31)
print(f"Last date of month is:", res.date())

Output:

The original date is: 2202-09-13
Last date of month is: 2202-09-30

Get Last Day of a Previous Month

• Import the datetime and timedelta class from a datetime module
• First, calculate the first day of a month using res = input_dt.replace(day=1).
• Now, use the timedelta class to subtract one day from the resultant date to get the last day of the previous month.

Example:

from datetime import datetime, timedelta

input_dt = datetime(2022, 9, 13)
first = input_dt.replace(day=1)
print('first day of a month:', first.date())

res = first - timedelta(days=1)
print('Last day of a previous month is:', res.date())

Output:

first day of a month: 2022-09-01
Last day of a previous month is: 2022-08-31

Get Last Day of a Next Month

1. Import the datetime and timedelta class from a datetime module
2. Next, use the day parameter of a timedelta class to replace the date’s day number with the 28 (because each month contains at least 28 days) to move to the next month
3. Next, use the timedelta class to add four days to the new date. By doing this, you will get the next month.
4. Repeat the 2 and 3 steps to get the second next month.
5. Now, use the timedelta class to subtract one day from the resultant date to get the last day of the next month.

Example:

from datetime import datetime, timedelta

input_dt = datetime(2022, 9, 13)
print('Input date:', input_dt.date())

# move to first next month
next_month = input_dt.replace(day=28) + timedelta(days=4)

# Now move to the second next month
next_month = next_month.replace(day=28) + timedelta(days=4)

# come back to the first next month's last day
res = next_month - timedelta(days=next_month.day)
print('Last day of the next month:', res.date())

Output:

Input date: 2022-09-13
Last day of the next month: 2022-10-31