Errors in calculating the Effective Annual Rate of a loan

CFA Level III
#1

This is a list of errors I made again and again (after 2 months or so):

  1. miss DAYS/360 in calculating the future value of put options premium. 2, miss DAYS/360 in calculating the interest income earned. 3, miss DAYS/360 in calculating the options payoff. 4, miss the spread in the lending rate.
#2

one thing i find helpful with the days/360 issue is to draw a time line…it reminds me that interest is paid over time (i.e from expiration date to repayment date)