ValueError: Time Data Does Not Match Format

Why This Happens

datetime.strptime() parses strings using format codes. If the format does not match, parsing fails. Common mistakes include using %m/%d/%Y for ISO dates (which use %Y-%m-%d).

The Problem

from datetime import datetime
dt = datetime.strptime('2024-01-15', '%m/%d/%Y')

The Fix

from datetime import datetime
dt = datetime.strptime('2024-01-15', '%Y-%m-%d')

# Or use dateutil for auto-detection:
from dateutil.parser import parse
dt = parse('2024-01-15')

Step-by-Step Fix

1. 1

   Match format exactly

   Compare date string with format string character by character.

2. 2

   Use common codes

   %Y=4-digit year, %m=month, %d=day, %H=hour, %M=minute.

3. 3

   Use dateutil

   pip install python-dateutil for automatic format detection.