Python - Dates & Time

Overview

Estimated time: 20–30 minutes

Use datetime and zoneinfo to work with timezone-aware timestamps and format/parse dates safely.

Learning Objectives

• Create naive and aware datetimes; convert timezones.
• Format and parse with strftime/strptime.
• Use timedelta for arithmetic.

Prerequisites

• Python - Standard Library Highlights

Creating and converting

from datetime import datetime, timezone
from zoneinfo import ZoneInfo

now_utc = datetime.now(timezone.utc)
now_ny = now_utc.astimezone(ZoneInfo("America/New_York"))
print(now_utc.isoformat())
print(now_ny.isoformat())

Formatting and parsing

from datetime import datetime
s = "2025-09-05 12:34:00"
dt = datetime.strptime(s, "%Y-%m-%d %H:%M:%S")
print(dt.strftime("%b %d, %Y %I:%M %p"))

Arithmetic

from datetime import datetime, timedelta
start = datetime(2025, 1, 1)
end = datetime(2025, 2, 1)
print((end - start).days)  # 31
print(start + timedelta(days=10))

Common Pitfalls

• Using naive datetimes in multi-timezone apps; prefer timezone-aware.
• Hardcoding timezone offsets; use zoneinfo for DST safety.

Checks for Understanding

1. How do you make a datetime timezone-aware?
2. Which module provides IANA timezones in Python 3.9+?

Exercises

1. Parse a timestamp string and convert it to UTC.
2. Compute the duration between two user-supplied dates in days.