Dates and times

Every application that logs, schedules, or processes data eventually has to deal with time — and time is a surprisingly large topic. Python's datetime module is adequate but lean; most of the footguns come from the interaction between naive and time-zone-aware datetimes, parsing inconsistent inputs, and DST transitions. This guide covers the mechanics, the idioms, and the traps.

Start here

If you're new to datetime, work through the Learn section in order — three short notebooks, around fifteen to twenty minutes each. Every code cell can be edited and run in place, directly on the page; no install required.

If you already know the basics and are looking for a specific technique, jump to the Recipes section, or scan the Reference for format codes and common patterns.

What this guide covers

Learn — date, time, datetime, and timedelta; parsing and formatting with ISO 8601 and strptime/strftime; time zones with zoneinfo.

Recipes — parsing a messy date column, computing durations and ages, converting between time zones, and avoiding common mistakes.

Reference — the full table of strftime/strptime format codes, timedelta arithmetic patterns, and zoneinfo usage.

Concepts — why naive datetimes are a footgun, and the "UTC everywhere" design rule (and when it doesn't apply).