If you enter a date with a two-digit year, JMP uses internal algorithms to assign the century. The sections below provide more details. How JMP Handles Dates Using Date Formats within JMP When you assign a date format to a numeric column in JMP, JMP stores the date internally as a signed, 64-bit integer representing the number of seconds since midnight on January 1, 1904. This enables date columns to be sorted and compared. As a user, you decide how to display the date.
Additional formats are available for both date and time values.
Because of their internal representation, the dates appear in their sorted order with the year 1999 appearing before the year 2000. Entering a Two-Digit Year JMP software running under Macintosh, Release 3.0 or later, and JMP software running under Windows, Release 3.2.5 or later, relies on the Macintosh date and time algorithms to assign the century. Specific rules apply to the input year when the current year falls within the first or last decade of the century. If the current year is between 1990 and 1999 inclusive and the input year is 10 or less, the year is assigned between 2000 and 2010. Conversely, if the input year is greater than 10, the year is assigned between 1911 and 1999.