People often tell me the day they were born to test my memory, and after telling them the day of the week, I love to turn the tables and ask them about their 21st birthday. The context of a memory helps fill in details that may, at first, be a little hazy. When you recall the day of the week an event took place, everything else starts to make more sense. Even though my mind has automatically stored that my 21st birthday was on a Friday, yours doesn't have to. Find the day of the week of your 21st birthday by Googling the date. Just knowing how long you had to wait for a weekend or how quickly you were back at school or work after your night of partying will help unlock details that you didn't remember were in there.