Many dates were reformatted with the File Expansion Project (FEP) in 2014, and on the files that were actually expanded, dates new use a standard date format of CCYY-MM-DD (yes, that’s including the dashes).  You’ll sometimes hear it by the term “ISO format” (which refers to the International Organization for Standardization).
 
When you choose from a list of fields in Query, you’ll see an “L” in the right-hand column under “Decimal.”  That just indicates the field is a date, rather than a straight numeric or alphanumeric field.  The cool thing about this format is that you do not need to do any formatting to get the date to appear properly in a Query, and you can do math on dates (such as to calculate the difference in days between one date and another date). 
 
However, only the dates in expanded account and transaction database tables use this new format.  Dates in other tables may still use older formats such as 6 digits mmddyy or yyddmm, including dates in the MASTER membership and non-member tables.  Those dates will be addressed later as part of M-Up.  And even after M-Up is done there will still be many smaller, ancillary database tables using older formats for the foreseeable future.