The Alarm That Slept In — Python Bug Hunt

Briefing

Inspired by the iPhone alarm bugs that made global news two New Years in a row — recurring alarms simply didn't fire when the date math wrapped wrong.

alarm.py: given the current time and a daily alarm time, return the minutes until it next fires. An alarm set for right now fires now (0 minutes).

Bug report

BUG-0700 · Priority: Everyone overslept · Reported by: the internet

minutes_until(now_h, now_m, alarm_h, alarm_m):

• alarm later today -> simple difference
• alarm earlier than now -> wraps to tomorrow
• alarm exactly now -> 0

Observed: alarms earlier in the day return NEGATIVE minutes, and the scheduler treats negatives as "never".

Logs

[alarm] now=23:30 alarm=07:00 -> -990 minutes -> skipped

The code as shipped

src/clock/alarm.py (editable)

# Minutes until the daily alarm next fires.

def minutes_until(now_h, now_m, alarm_h, alarm_m):
    now = now_h * 60 + now_m
    alarm = alarm_h * 60 + alarm_m
    return alarm - now