I've been using both PC and mobile as my alarm clock for some time. The alarm program on PC can memorize my settings and ring automatically on every Monday to Friday. The downside is that when a weekday is holiday (or my day-off).
On my mobile, however, I've to set alarm manually every night. It has a little feature, a bonus, it tells you how many hours and minutes left. And most of the time, I got 5 or 6, sometimes 4.
Some days ago I got an 8. But an hour before the time came, I woke up.
Tonight it is a 6 something. And after finishing this post, it's 5 somethings.