How to parse a date string in Python
datetime.strptime(s, fmt) parses a specific format. datetime.fromisoformat(s) parses ISO 8601 with no format arg needed.
from datetime import datetime
dt = datetime.strptime("2026-08-01", "%Y-%m-%d")
print(dt) # 2026-08-01 00:00:00
iso = datetime.fromisoformat("2026-08-01T15:30:00+00:00")
print(iso) # 2026-08-01 15:30:00+00:00strptime is the inverse of strftime — same format codes. When the input string matches your format exactly, you get a datetime back; on any mismatch it raises ValueError.
For ISO 8601 strings (dates from APIs, JSON payloads, most modern systems), datetime.fromisoformat is the winning shortcut — no format string needed, handles the timezone offset correctly, and is faster than strptime.
For fuzzy human-typed input ('July 4th, 2026', 'yesterday'), reach for the third-party dateutil.parser.parse — it accepts almost anything but is 100x slower than strptime, so use it only where you need the flexibility.
Variations
ISO 8601 with fromisoformat
from datetime import datetime
dt = datetime.fromisoformat("2026-08-01T15:30:00+00:00")Python 3.11+ accepts every ISO variant including the trailing Z.
Format with 12-hour time
dt = datetime.strptime("08/01/2026 03:30 PM", "%m/%d/%Y %I:%M %p")%I is 12-hour, %p is AM/PM.
Fuzzy human input
from dateutil.parser import parse
parse("Aug 1st, 2026 at 3:30 PM")Requires pip install python-dateutil. Slower but far more forgiving.
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