Python Date Operations

Date arithmetic, formatting, and comparison utilities for Python datetime objects

Python Date Operations

Working with dates in Python is straightforward with the datetime module. These utilities simplify common date operations like calculating differences, adding days, and checking date properties.

Calculate Date Differences

Calculate the difference between two dates in days, months, or years:

from datetime import date
from math import ceil

def days_diff(start, end):
  return (end - start).days

def months_diff(start, end):
  return ceil((end - start).days / 30)

def years_diff(start, end):
  return ceil((end - start).days / 365)

days_diff(date(2020, 10, 25), date(2020, 10, 28)) # 3
months_diff(date(2020, 10, 25), date(2020, 11, 25)) # 1
years_diff(date(2020, 10, 25), date(2021, 10, 25)) # 1

Calculate Relative Dates

Days Ago

Calculate a date n days in the past:

from datetime import timedelta, date

def days_ago(n):
  return date.today() - timedelta(n)

days_ago(5) # date(2020, 10, 23)

Days From Now

Calculate a date n days in the future:

from datetime import timedelta, date

def days_from_now(n):
  return date.today() + timedelta(n)

days_from_now(5) # date(2020, 11, 02)

Add Days to a Date

Add days to any date:

from datetime import date, datetime, timedelta

def add_days(n, d = datetime.today()):
  return d + timedelta(n)

add_days(5, date(2020, 10, 25)) # date(2020, 10, 30)
add_days(-5, date(2020, 10, 25)) # date(2020, 10, 20)

Subtract Days from a Date

Subtract days from any date:

from datetime import date, datetime, timedelta

def subtract_days(n, d = datetime.today()):
  return d - timedelta(n)

subtract_days(5, date(2020, 10, 25)) # date(2020, 10, 20)
subtract_days(-5, date(2020, 10, 25)) # date(2020, 10, 30)

Check Date Properties

Check if Date is Weekend

from datetime import datetime, date

def is_weekend(d = datetime.today()):
  return d.weekday() > 4

is_weekend(date(2020, 10, 25)) # True
is_weekend(date(2020, 10, 28)) # False

Check if Date is Weekday

from datetime import datetime, date

def is_weekday(d = datetime.today()):
  return d.weekday() <= 4

is_weekday(date(2020, 10, 25)) # False
is_weekday(date(2020, 10, 28)) # True

Practical Use Cases

Calculate Age

from datetime import date

def calculate_age(birth_date):
  today = date.today()
  return years_diff(birth_date, today)

birth_date = date(1990, 5, 15)
age = calculate_age(birth_date)  # Current age

Check Subscription Expiry

from datetime import date

subscription_end = date(2024, 12, 31)
today = date.today()
days_remaining = days_diff(today, subscription_end)

if days_remaining < 0:
    print("Subscription expired")
elif days_remaining < 7:
    print(f"Subscription expires in {days_remaining} days")
else:
    print("Subscription is active")

Business Day Calculations

from datetime import date, timedelta

def add_business_days(start_date, days):
  current = start_date
  added = 0
  
  while added < days:
    current = add_days(1, current)
    if is_weekday(current):
      added += 1
  
  return current

order_date = date(2024, 1, 15)  # Monday
delivery_date = add_business_days(order_date, 5)  # 5 business days later

Date Range Generation

from datetime import date

def date_range(start, end):
  dates = []
  current = start
  
  while current <= end:
    dates.append(current)
    current = add_days(1, current)
  
  return dates

start = date(2024, 1, 1)
end = date(2024, 1, 7)
week = date_range(start, end)
# [date(2024, 1, 1), date(2024, 1, 2), ..., date(2024, 1, 7)]

Report Date Filtering

from datetime import date

# Get dates for last 30 days
end_date = date.today()
start_date = days_ago(30)

# Filter records
records = get_all_records()
recent_records = [
    r for r in records 
    if start_date <= r['date'] <= end_date
]

Scheduled Task Checker

from datetime import date

def should_run_task(last_run_date, interval_days):
  next_run = add_days(interval_days, last_run_date)
  return date.today() >= next_run

last_backup = date(2024, 1, 1)
if should_run_task(last_backup, 7):
    print("Time to run weekly backup")

Weekend/Weekday Event Pricing

from datetime import date

def get_ticket_price(event_date):
  base_price = 50
  if is_weekend(event_date):
    return base_price * 1.5  # 50% weekend surcharge
  return base_price

event = date(2024, 2, 10)  # Saturday
price = get_ticket_price(event)  # 75.0

Next Steps

Lists

Learn about list operations

Dictionaries

Explore dictionary operations