Duration until a given date

duration.ex

def time_until_reset() do
  today = :erlang.date()
  now = :erlang.time()
  now_in_sec = :calendar.datetime_to_gregorian_seconds({today, now})
  days_until_next_monday = 8 - :calendar.day_of_the_week(today)

  midnight = {0, 0, 0}

  next_monday_in_sec =
    :calendar.datetime_to_gregorian_seconds(
      {(:calendar.date_to_gregorian_days(today) + days_until_next_monday)
       |> :calendar.gregorian_days_to_date(), midnight}
    )

  sec_diff = next_monday_in_sec - now_in_sec
  hour_duration = 60 * 60
  hours = Integer.floor_div(sec_diff, hour_duration)
  minute_duration = 60
  minutes = Integer.floor_div(sec_diff - hour_duration * hours, minute_duration)
  seconds = sec_diff - (hours * hour_duration + minutes * minute_duration)

  {hours, minutes, seconds}
end