from datetime import datetime


def length_of_storage_time_in_seconds(now):
    """
    calculate how long, in seconds, is left before 20mins past the current, or next hour
    :return: the number of seconds before 20mins past the current, or next, hour
    """

    minute = now.minute
    if 0 < minute <= 20:
        return (20 - minute) * 60
    mins_to_hour = 60 - minute
    return (mins_to_hour + 20) * 60