Parse and Format Datetimes with Python datetime Module

Question

Given two date strings '2026-01-15T09:30:00Z' and '2026-02-10T18:00:00Z', parse them using Python's standard `datetime` module and calculate the full calendar days elapsed between them.

Accepted Answer

Optimal Solution:
from datetime import datetime

def days_between(start_str: str, end_str: str) -> int:
    # Python 3.11+ handles trailing 'Z' directly in fromisoformat
    dt1 = datetime.fromisoformat(start_str.replace('Z', '+00:00'))
    dt2 = datetime.fromisoformat(end_str.replace('Z', '+00:00'))
    delta = dt2 - dt1
    return delta.days

Technical Explanation:
`datetime.fromisoformat()` is modern and much faster than `strptime()`. Subtracting datetimes yields a `timedelta` object whose `.days` property gives calendar day differences.