I can count on one hand the times I've overslept. The few times it have happened it have been because of a malfunctioning clock or something else, not that I've turned off the alarm and continued to sleep.
As of yesterday morning I can now add another "incident" to my list. God knows how, but somehow I had managed to change the time on my alarm with one hour. So when the alarm went of at 6 it was already 7. I did though wake up about at 5:15 (alarm time) and glanced at the clock knowing that it wasn't time to get up yet. Well, my internal clock was actually right since it was 6:15.
I did my usual morning routine, breakfast, shower and so on. The radio was on as usual as well. I always look at my mobile phone before putting it in my handbag and when time time said 7:50 I just starred at the screen. Couldn't be right. Went in to the kitchen. Clock on wall said 7:50 and clock on the microwave said 7:50. Back in the bedroom I looked at the alarm which said 6:50 and when I checked the clock on the computer I realized I was defeated and very much one hour late.
Since I didn't have any meetings until 10 I just decided to live with it and keep going with my normal routine. I arrived at office right before 9 and felt rather relaxed actually. I have been missing that hour all day though. That hour between 8 and 9 is my catch-up-on-things and prepare-for-the-day hour while drinking some more coffee. Now I just had to get going immediately.
Last night I changed the batteries my alarm preventing another late morning (worked) and hopefully it will be another 10-15 years until I oversleep again.