Dates & Times Competent¶

🐍 Core Python Track · Level 2

⏱️ ~2 days 📚 Prerequisite: Standard Library

The datetime module handles dates and times; zoneinfo (3.9+) adds real timezone support from the system's IANA database.

Building dates and times¶

Building dates and times in Dates & Times — what it is and when to use it.

from datetime import date, datetime, time

d = date(2026, 1, 15)
print(d.year, d.month, d.day)   # 2026 1 15
print(d.weekday())              # 3  (Mon=0 ... Thu=3)

dt = datetime(2026, 1, 15, 9, 30, 0)
print(dt.hour, dt.minute)       # 9 30

Formatting (`strftime`) and parsing (`strptime`)¶

Formatting (strftime) and parsing (strptime) in Dates & Times — what it is and when to use it.

from datetime import datetime

dt = datetime(2026, 1, 15, 9, 5)
print(dt.strftime("%Y-%m-%d %H:%M"))        # 2026-01-15 09:05
print(dt.strftime("%A, %B %d"))             # Thursday, January 15

parsed = datetime.strptime("2026-01-15", "%Y-%m-%d")
print(parsed.date())                        # 2026-01-15

Common codes: %Y year, %m month, %d day, %H hour, %M minute, %S second, %A weekday name, %B month name.

ISO format (preferred for storage/exchange)¶

ISO format (preferred for storage/exchange) in Dates & Times — what it is and when to use it.

from datetime import datetime

dt = datetime(2026, 1, 15, 9, 5, 0)
print(dt.isoformat())                       # 2026-01-15T09:05:00
print(datetime.fromisoformat("2026-01-15T09:05:00").hour)   # 9

Arithmetic with `timedelta`¶

Arithmetic with timedelta in Dates & Times — what it is and when to use it.

from datetime import datetime, timedelta

dt = datetime(2026, 1, 15, 12, 0)
print((dt + timedelta(days=7)).date())      # 2026-01-22
print((dt - timedelta(hours=3)).hour)       # 9

delta = datetime(2026, 1, 20) - datetime(2026, 1, 15)
print(delta.days)                           # 5
print(delta.total_seconds())                # 432000.0

Timezone-aware datetimes with `zoneinfo`¶

Timezone-aware datetimes with zoneinfo in Dates & Times — what it is and when to use it.

Naive datetimes have no timezone; aware ones carry a tzinfo. Prefer aware for anything real-world.

from datetime import datetime
from zoneinfo import ZoneInfo

utc = datetime(2026, 1, 15, 12, 0, tzinfo=ZoneInfo("UTC"))
ny = utc.astimezone(ZoneInfo("America/New_York"))
print(ny.hour)                 # 7  (UTC-5 in January)
print(utc.tzinfo)              # UTC
print(ny.utcoffset().total_seconds() / 3600)   # -5.0

Unix timestamps¶

Unix timestamps in Dates & Times — what it is and when to use it.

from datetime import datetime, timezone

dt = datetime(2026, 1, 15, tzinfo=timezone.utc)
ts = dt.timestamp()
print(datetime.fromtimestamp(ts, tz=timezone.utc).year)   # 2026

Naive vs aware

You cannot subtract an aware datetime from a naive one — it raises TypeError. Pick one convention (ideally UTC-aware) and convert at the edges of your system.

Practice exercises¶

Compute how many days until a given future date.
Parse "15/01/2026 09:30" with the right strptime format.
Convert a UTC datetime to three different timezones with zoneinfo.
Given two ISO datetime strings, print the duration between them in hours.

💬 Discussion

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