def get_dayobs(fits_dict: dict):
    """
    Get dayobs from a fits_dict
    :param fits_dict: Fits dictionary with required header keywords
    :return: Date in DAY-OBS YYYYMMDD format
    """
    day_obs = fits_dict.get('DAY-OBS')
    if not day_obs:
        date_obs = fits_dict.get('DATE-OBS')
        day_obs = date_obs.split('T')[0].replace('-', '')
    return day_obs
