Paris Time

Since my cell phone is a rental, I can't be bothered to read the instruction book.  Well, let's face it -- I don't read the instruction book in English either.  But therefore, I cannot figure out how to program the clock on it.  Luckily, the minutes are correct.  But it's 10 hours ahead.  Since it's a European-style 24-hour clock, in the mornings, my clock reads 19:45, when it's 9:45.  But in the afternoons, it reads 3:45 when it's 5:45 (which is 17:45).  So I have devised an elaborate system whereby I subtract 10 hours from numbers 10 up to 23, but add 2 hours from numbers 0 to below 10.  Then  in the afternoon, I must add 12 hours to figure out the equivalent time on the 24 hour clock.  And finally, I need to subtract 6 hours for contacting my family on the East Coast, and 9 hours for contacting people on the West Coast.  Got that?  Subtract 10, add 12, then subtract 9, or else add 2, add 12, subtract 9, so that I can know if it's a good time to contact you in San Francisco.  Or something like that.

Meanwhile, I have not ever been late for the girls' school drop off or pick up.  And only once did we mistakenly show up for an activity a full hour early.  I would like to publicly thank all my math teachers.