def get_build_timestamp(*, pages: Collection[Page] | None = None) -> int:
    """
    Returns the number of seconds since the epoch for the latest updated page.

    In reality this is just today's date because that's how pages' update time is populated.
    """
    if pages:
        # Lexicographic comparison is OK for ISO date.
        date_string = max(p.update_date for p in pages)
        dt = datetime.fromisoformat(date_string).replace(tzinfo=timezone.utc)
    else:
        dt = get_build_datetime()
    return int(dt.timestamp())

    Returns the number of seconds since the epoch for the latest updated page.

    In reality this is just today's date because that's how pages' update time is populated.
    
mkdocs/utils/__init__.py