AA is short for Armed Forces of the Americas - all branches of the military forces of the United States (Army, Air Force, Coast Guard, Marine Corps and Navy). APO is short for Army Post Office, which is part of the Military Postal System; it serves land-based military personnel (typically Army and Air Force). FPO is short for Fleet Post Office and serves water-based soldiers (typically the Navy, Marine Corps and Coast Guard).
Count distinct values in Excel (unique and 1st duplicate occurrences) To get a count of distinct values in a list, use the following formula: =SUM(1/COUNTIF(range, range)) Remember, it's an array formula, and therefore you should press the Ctrl + Shift + Enter shortcut instead of the usual Enter keystroke.
Date is being treated specially in Excel. The format you see in Excel worksheet such as dd/mm/yyyy is only a displayed formatting, the underlying value of a Date is a numeric value. 1/1/1900 is considered as the first date in Excel, the numeric value of it is 1, and add one to each day onwards.