from __future__ import annotations

from datetime import UTC, datetime


def utcnow() -> datetime:
    return datetime.now(UTC)


def iso(dt: datetime | None) -> str | None:
    if dt is None:
        return None
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=UTC)
    return dt.astimezone(UTC).isoformat().replace("+00:00", "Z")