from datetime import datetime, timedelta
from typing import Optional
import pytz


def utcnow() -> datetime:
    """Get current UTC datetime."""
    return datetime.now(pytz.UTC)


def parse_date(date_str: str) -> datetime:
    """Parse date string to datetime."""
    formats = ["%Y-%m-%d", "%Y-%m-%dT%H:%M:%S", "%Y-%m-%d %H:%M:%S"]
    for fmt in formats:
        try:
            return datetime.strptime(date_str, fmt)
        except ValueError:
            continue
    raise ValueError(f"Unable to parse date: {date_str}")


def format_timestamp(dt: datetime, format_str: str = "%Y-%m-%dT%H:%M:%S") -> str:
    """Format datetime to string."""
    return dt.strftime(format_str)


def calculate_time_delta(start: datetime, end: datetime) -> timedelta:
    """Calculate time delta between two datetimes."""
    return end - start


def safe_divide(a: float, b: float, default: float = 0.0) -> float:
    """Safely divide two numbers with default fallback."""
    if b == 0:
        return default
    return a / b