from datetime import datetime, timedelta

def process_dates(date):
    """
    Process adjacent days to account for flights that
    have a different departure day than the day they were
    archived (which is the date contained in the filenames)
    """

    """
    Convert to datetime objects before processing
    This is done so the conversion is less error-prone by
    avoiding edge cases like 1st of Jan, 29th of Feb, y3k, etc
    """
    datetimes = []
    today = datetime.strptime(date, '%Y%m%d')

    """
    Compute the adjacent days, but keeping the order of the elements
    the following: today, yesterday, tomorrow, and the day after tomorrow.
    This is done because the looking up later on is done sequentially
    and the order reflects the probability of being the needed date
    (i.e. it's most probable the needed day is today, so it will stop before
    processing the other days)
    """
    [datetimes.append(today + timedelta(days=i)) for i in [0, -1, 1, 2]]
    return [datetime.strftime(j, '%y%m%d') for j in datetimes]