Date and Time

🕰️ Python Date and Time: Your Time Travel Toolkit

Imagine you have a magical watch that can remember any moment, jump forward or backward in time, and even understand what time it is anywhere in the world. That’s exactly what Python’s datetime module gives you!

🎯 The Big Picture

Think of dates and times like LEGO blocks:

• Date = A calendar page (year, month, day)
• Time = A clock face (hour, minute, second)
• DateTime = Both together - a complete moment in time!

from datetime import date, time, datetime

📅 Creating Dates and Times

Making a Date (Like Picking a Calendar Page)

Remember your birthday? Let’s tell Python about it:

from datetime import date

# Create a specific date
my_birthday = date(2020, 5, 15)
# Year=2020, Month=5, Day=15

print(my_birthday)  # 2020-05-15

What Day Is Today?

from datetime import date

today = date.today()
print(today)  # Shows today's date!

# Get the pieces
print(today.year)   # 2024
print(today.month)  # 12
print(today.day)    # 1

Making a Time (Like Setting an Alarm)

from datetime import time

# Wake up time: 7:30 AM
wake_up = time(7, 30, 0)
# Hour=7, Minute=30, Second=0

print(wake_up)  # 07:30:00

DateTime: The Complete Package

from datetime import datetime

# A specific moment
party_time = datetime(2024, 12, 25, 18, 30)
# Christmas Day at 6:30 PM

print(party_time)  # 2024-12-25 18:30:00

# Right now!
now = datetime.now()
print(now)  # Current date AND time

🎨 Date and Time Formatting

Your dates are like clay - you can shape them however you want!

The Magic of strftime()

strftime = “string from time” (turn time into readable text)

from datetime import datetime

now = datetime.now()

# Different styles
print(now.strftime("%B %d, %Y"))
# December 01, 2024

print(now.strftime("%m/%d/%y"))
# 12/01/24

print(now.strftime("%A"))
# Sunday

🔤 Format Code Cheat Sheet

Real Examples

from datetime import datetime

dt = datetime(2024, 7, 4, 14, 30)

# American style
print(dt.strftime("%m/%d/%Y"))
# 07/04/2024

# European style
print(dt.strftime("%d-%m-%Y"))
# 04-07-2024

# Friendly format
print(dt.strftime("%B %d at %I:%M %p"))
# July 04 at 02:30 PM

📖 Parsing Date Strings

Sometimes dates come as text. We need to turn them back into real dates!

The Magic of strptime()

strptime = “string parse time” (read time from text)

from datetime import datetime

# Text becomes a real datetime!
text = "2024-12-25"
christmas = datetime.strptime(text, "%Y-%m-%d")

print(christmas)  # 2024-12-25 00:00:00
print(type(christmas))  # <class 'datetime.datetime'>

Different Text Formats

from datetime import datetime

# American format
date1 = datetime.strptime(
    "12/25/2024",
    "%m/%d/%Y"
)

# With time
date2 = datetime.strptime(
    "Dec 25, 2024 3:30 PM",
    "%b %d, %Y %I:%M %p"
)

# European format
date3 = datetime.strptime(
    "25-12-2024",
    "%d-%m-%Y"
)

⚠️ Watch Out!

The format string MUST match the text exactly:

# This works
datetime.strptime("2024-12-25", "%Y-%m-%d")

# This CRASHES - wrong format!
# datetime.strptime("2024-12-25", "%m/%d/%Y")

⏱️ timedelta: Time Math Magic

What if you could add or subtract time like numbers?

What is timedelta?

timedelta = a chunk of time you can add or remove

from datetime import timedelta

# Create time chunks
one_day = timedelta(days=1)
one_week = timedelta(weeks=1)
two_hours = timedelta(hours=2)

Adding Time (Into the Future!)

from datetime import datetime, timedelta

today = datetime.now()

# One week from now
next_week = today + timedelta(weeks=1)

# 3 days and 5 hours later
later = today + timedelta(days=3, hours=5)

print(f"Today: {today}")
print(f"Next week: {next_week}")

Subtracting Time (Back to the Past!)

from datetime import datetime, timedelta

today = datetime.now()

# One week ago
last_week = today - timedelta(weeks=1)

# Yesterday
yesterday = today - timedelta(days=1)

print(f"Yesterday: {yesterday}")

Finding the Gap Between Dates

from datetime import date

birthday = date(2024, 5, 15)
today = date(2024, 12, 1)

# Subtract to get timedelta
gap = today - birthday

print(gap.days)  # 200 days!
print(gap)  # 200 days, 0:00:00

🎯 Real-World Example: Age Calculator

from datetime import date

def days_until_birthday(birth_month, birth_day):
    today = date.today()
    next_bday = date(today.year, birth_month, birth_day)

    if next_bday < today:
        next_bday = date(today.year + 1, birth_month, birth_day)

    days_left = (next_bday - today).days
    return days_left

print(days_until_birthday(5, 15))
# Days until May 15!

🌍 Timezone Handling

It’s 3 PM in New York but 8 PM in London. How do we handle this?

The Problem: Naive vs Aware

graph TD
    A["datetime"] --> B["Naive"]
    A --> C["Aware"]
    B --> D["No timezone info"]
    B --> E["Like a clock with no location"]
    C --> F["Has timezone info"]
    C --> G["Knows where in the world"]

Using timezone (Built-in)

from datetime import datetime, timezone, timedelta

# UTC = Universal Time (London in winter)
utc_now = datetime.now(timezone.utc)
print(utc_now)

# Create a timezone offset
# New York is UTC-5
ny_tz = timezone(timedelta(hours=-5))
ny_time = datetime.now(ny_tz)
print(ny_time)

The Better Way: zoneinfo (Python 3.9+)

from datetime import datetime
from zoneinfo import ZoneInfo

# Create timezone-aware times
ny = ZoneInfo("America/New_York")
tokyo = ZoneInfo("Asia/Tokyo")

now_ny = datetime.now(ny)
now_tokyo = datetime.now(tokyo)

print(f"New York: {now_ny}")
print(f"Tokyo: {now_tokyo}")

Converting Between Timezones

from datetime import datetime
from zoneinfo import ZoneInfo

# Start with New York time
ny_tz = ZoneInfo("America/New_York")
ny_time = datetime(2024, 12, 1, 9, 0, tzinfo=ny_tz)

# Convert to Tokyo time
tokyo_tz = ZoneInfo("Asia/Tokyo")
tokyo_time = ny_time.astimezone(tokyo_tz)

print(f"NY: {ny_time}")
# NY: 2024-12-01 09:00:00-05:00

print(f"Tokyo: {tokyo_time}")
# Tokyo: 2024-12-01 23:00:00+09:00

Making Naive Datetime Aware

from datetime import datetime
from zoneinfo import ZoneInfo

# Naive (no timezone)
naive = datetime(2024, 12, 1, 12, 0)

# Add timezone info
london = ZoneInfo("Europe/London")
aware = naive.replace(tzinfo=london)

print(aware)
# 2024-12-01 12:00:00+00:00

🚀 Quick Reference

from datetime import date, time, datetime, timedelta, timezone
from zoneinfo import ZoneInfo  # Python 3.9+

# CREATE
today = date.today()
now = datetime.now()
specific = datetime(2024, 12, 25, 18, 30)

# FORMAT (datetime → string)
now.strftime("%Y-%m-%d")

# PARSE (string → datetime)
datetime.strptime("2024-12-25", "%Y-%m-%d")

# TIME MATH
future = now + timedelta(days=7)
past = now - timedelta(hours=3)
gap = date2 - date1  # Returns timedelta

# TIMEZONES
utc_time = datetime.now(timezone.utc)
aware = now.replace(tzinfo=ZoneInfo("UTC"))
converted = aware.astimezone(ZoneInfo("Asia/Tokyo"))

🎉 You Did It!

You now have a time machine in your pocket! You can:

• ✅ Create any date or time you need
• ✅ Format dates in any style
• ✅ Read dates from text
• ✅ Do math with time (add, subtract, compare)
• ✅ Handle timezones like a pro

Remember: Dates are just numbers wearing fancy clothes. Once you understand the pattern, you can style them however you want! 🕐✨