"""Determine if a period is truly annual (300-400 days).

Annual periods should be approximately one year, allowing for:
- Leap years (366 days)
- Slight variations in fiscal year end dates
- But rejecting multi-year cumulative periods

Args:
    period (Dict): A dictionary containing 'start_date' and 'end_date' keys with date strings in 'YYYY-MM-DD' format.

Returns:
    bool: True if the period duration is between 300 and 400 days (inclusive), False otherwise or if an error occurs.
"""