Probability, mindlessness and periodicity

I bought my current cell phone in mid January 2008, which means I have had it for ~830 days.

I tend not to lose sight of the few things I keep on me at all times - Keys, wallet and cell phone. In this 830 day period, I doubt I have forgotten my phone for more than three days. Ok, lets just add some extra five days, for times I have travelled without the phone charger, resulting in me not having a phone available. So, eight days out of 830 gives us that the probability for me accidentally not having access to my phone for a whole day is close to 0.01, or 1% ⇒ P(stupid) ≅ 0.01.

I am not a heavy phone user. Far from it, I tend not to like using the phone. My calls are always kept to the minimum necessary, and I would not be surprised if I used my phone typically less than twice per week. However, there is a recurring event that makes my phone ring more often during certain very well defined periods of the year, with 1/365 probability. So, lets call this P(birthday) ≅ 0.00273.

Yesterday I spent the day with some good, very long time friends. We did the April Ciclotón - I biked for 42 very nice kilometers, they did 36 (as we met 8Km away from my home ;-) )... but yes, after a while, I left my phone at my friends' table.

So I guess today the phone will ring way more insistently than usual. At a table far away from home. With a probability of P(stupid ∩ birthday) ≅ 2.73 × 10⁻⁵.

So I'm facing the enjoyment of a very improbable day!