I happen to have always had an excellent memory for dates (I can tell you what date my dog had puppies in 1952), but in the case of escort appts, I maintained a list of everyone I hired and the price paid, in case the activity became tax deductible . Even so, the really special ones stuck in my mind, so I remembered that it was 1987 [i did have to look up the exact date]. I also have kept a daily journal for the past 45 years, in which I can look up more details, like his address, what he looked like, what we did, etc., among the record of everything else that happened that day.