The Calendar Trick
If you give me your date of birth I can tell you the day of the week on which you were born. Some information: This was a presentation for a job in Cryptography, hence the punchline about Enigma. I got the job. Not mentioned in the video, if it's January or February of a leap year we need to subtract 1 (since we are counting leap days). If I'm counting from 1899 why do I add 41 instead of 42? Because the date must be at least 1 - that automatically pushes us into 1900 and we count the years from there. The sound is rubbish because Vista is giving me problems.