def format_exif_timezone_offset(offset: int) -> str:
    """
    Serializes a number of minutes to a EXIF time offset ("±HH:MM") string.
    """
    sign = 1 if offset >= 0 else -1
    if sign == -1:
        offset = -offset
    sign_str = "+" if sign == 1 else "-"
    hours_str = str(offset // 60).zfill(2)
    minutes_str = str(offset % 60).zfill(2)
    return f"{sign_str}{hours_str}:{minutes_str}"