async def get_tz_offset(client, user_id):
    """
    Retrieve the (seconds as an integer) time zone offset from UTC for a user.
    Outputs an integer in the range [-43200, 43200]. (-12h, +12h.)

    client: the client from the context object.
    user_id: the human-opaque Slack user identifier.
    """
    # https://api.slack.com/methods/users.info
    res = await client.users_info(user=user_id)
    return res['user']['tz_offset']