Python: Calculate the first/last Monday, Tuesday, Wednesday, Thursday, Friday, Saturday or Sunday of the Month

Date calculation is pretty easy in Python, but to find the first/last specific day of the month may be a bit harder.

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01.import calendar

02. 

03.# Get the first "day" of the month and the number of days in the month

04.month_range = calendar.monthrange(your_date.year, your_date.month)

05. 

06.if offset_position == 'first': # First Monday of the month

07.  date_corrected = datetime.date(your_date.year, your_date.month, 1)

08.  delta = (calendar.MONDAY - month_range[0]) % 7

09.  return your_date_corrected + datetime.timedelta(days = delta)

10. 

11.else: # Last Monday of the month

12.  date_corrected = datetime.date(your_date.year, your_date.month, month_range[1])

13.  delta = (your_date.weekday() - calendar.MONDAY) % 7

14.  return your_date_corrected - datetime.timedelta(days = delta)

The snippet above will find the first or last Monday in the year/month given in "your_date". Throw it into a reusable function and you won't have to look at this problem again.

Now for more important things in life.

Sources

• datetime - In Python, how do I find the date of the first Monday of a given week?
• dates - Get Last Day of the Month in Python
• datetime - How to get the Python date object for last Wednesday