Python datetime Module Explained — Dates, Times, and Formatting

# First, let's import the specific classes we need from the datetime module.
# This cleaner import style avoids writing 'datetime.datetime' everywhere.
from datetime import date, time, datetime, timedelta

# --- date object: only year, month, day ---
release_date = date(2024, 11, 15)          # November 15, 2024
print("Release date:", release_date)        # Prints the date
print("Year:", release_date.year)           # Access individual parts
print("Month:", release_date.month)
print("Day:", release_date.day)

# --- time object: only hour, minute, second ---
store_opens = time(9, 30, 0)               # 9:30:00 AM
print("\nStore opens at:", store_opens)

# --- datetime object: date AND time together ---
user_login = datetime(2024, 11, 15, 14, 35, 22)  # Nov 15, 2024 at 2:35:22 PM
print("\nUser logged in at:", user_login)

# --- timedelta object: a duration (not a specific moment) ---
trial_period = timedelta(days=14)          # A 14-day free trial
print("\nTrial lasts:", trial_period)
print("Trial days:", trial_period.days)

from datetime import date, datetime

# Get today's date only (no time component)
today = date.today()
print("Today's date:", today)                  # e.g. 2024-11-15
print("Day of week (0=Mon, 6=Sun):", today.weekday())  # Monday=0, Sunday=6
print("Is today a weekday?", today.weekday() < 5)       # True if Mon-Fri

# Get the current full timestamp (date + time)
right_now = datetime.now()
print("\nFull timestamp:", right_now)           # e.g. 2024-11-15 14:35:22.123456
print("Current hour:", right_now.hour)          # Just the hour portion
print("Current minute:", right_now.minute)      # Just the minute portion

# Extract just the date part from a datetime object
login_timestamp = datetime(2024, 11, 15, 8, 45, 0)   # Simulated login time
login_date_only = login_timestamp.date()              # Strip away the time part
print("\nLogin timestamp:", login_timestamp)
print("Login date only:", login_date_only)

# Check if the login happened today
if login_date_only == date.today():
    print("User logged in today!")
else:
    print("Login was on a different day.")

from datetime import date, datetime, timedelta

# --- Scenario 1: Calculate when a free trial expires ---
trial_start = date(2024, 11, 1)         # Trial started November 1st
trial_duration = timedelta(days=30)     # Free trial lasts 30 days
trial_end = trial_start + trial_duration  # Add the duration to the start date
print("Trial started:", trial_start)
print("Trial ends:", trial_end)          # Should be December 1st

# --- Scenario 2: How many days until an event? ---
today = date.today()
new_year = date(2025, 1, 1)             # Next New Year's Day
days_until_new_year = new_year - today  # Subtracting two dates gives a timedelta
print("\nDays until New Year:", days_until_new_year.days, "days")

# --- Scenario 3: Check if a password is too old (security feature) ---
last_password_change = datetime(2024, 7, 20, 10, 0, 0)  # Changed July 20th
current_time = datetime.now()
password_age = current_time - last_password_change       # timedelta result
max_age = timedelta(days=90)                             # Force reset after 90 days

print("\nPassword age:", password_age.days, "days")
if password_age > max_age:
    print("WARNING: Password is too old! Please reset it.")
else:
    days_left = max_age - password_age
    print(f"Password OK. Must be changed in {days_left.days} days.")

# --- Scenario 4: total_seconds() for precise measurement ---
downtime_start = datetime(2024, 11, 15, 2, 0, 0)  # Server went down at 2:00 AM
downtime_end   = datetime(2024, 11, 15, 2, 47, 33) # Back up at 2:47:33 AM
downtime_duration = downtime_end - downtime_start
print(f"\nServer was down for {downtime_duration.total_seconds()} seconds")
print(f"That's {downtime_duration.seconds // 60} minutes and {downtime_duration.seconds % 60} seconds")

from datetime import datetime

right_now = datetime(2024, 11, 15, 14, 35, 22)  # A fixed datetime for consistent output

# --- strftime: datetime object --> formatted string ---
# Format codes: %Y=4-digit year, %m=month number, %d=day, %B=full month name,
#               %A=full weekday name, %H=hour(24h), %M=minute, %S=second

# Format for a European audience
europe_format = right_now.strftime("%d/%m/%Y")         # 15/11/2024
print("European format:", europe_format)

# Format for an American audience
usa_format = right_now.strftime("%m/%d/%Y")            # 11/15/2024
print("US format:", usa_format)

# A long, human-readable format
friendly_format = right_now.strftime("%A, %d %B %Y")  # Friday, 15 November 2024
print("Friendly format:", friendly_format)

# A format good for filenames (no slashes or spaces)
file_safe_format = right_now.strftime("%Y%m%d_%H%M%S") # 20241115_143522
print("Filename-safe format:", file_safe_format)

# Including the time
full_readable = right_now.strftime("%d %B %Y at %H:%M")
print("Full readable:", full_readable)

# --- strptime: formatted string --> datetime object ---
# Imagine reading a date from a web form or CSV file:
user_input_date = "25/12/2024"    # Christmas Day typed by a user

# Tell strptime exactly what format the string is in
parsed_date = datetime.strptime(user_input_date, "%d/%m/%Y")
print("\nParsed date object:", parsed_date)         # Now it's a real datetime
print("Type:", type(parsed_date))                  # Confirm it's a datetime object
print("Month number:", parsed_date.month)           # Access the month as a number
print("Day of week:", parsed_date.strftime("%A"))   # 'Wednesday'

# Real-world example: reading dates from a CSV log file
log_entry = "2024-11-15 08:45:00"   # Common log file timestamp format
parsed_log_time = datetime.strptime(log_entry, "%Y-%m-%d %H:%M:%S")
print("\nLog timestamp parsed:", parsed_log_time)
print("Log entry hour:", parsed_log_time.hour)