In STATISTICA, date values of variables are stored internally as a single integer value that represents the number of days that have passed since January 1, 1900. The specific conversion of integer values to dates and vice versa is also affected by the setting of the Use Excel-style Julian date format option located in the Spreadsheets options pane of the Options dialog.
For example, a date entered and displayed as 1/21/1968 is stored as 24858 (or 24856, depending on the setting of the Use Excel-style Julian date format option, see note).
Note: The Use Excel-style Julian date format option affects the way in which dates are interpreted and displayed when a date format is selected as the display format for variables. Specifically, the algorithm used in Microsoft Excel™ to convert Julian dates for display in conventional date formats (e.g., April 24, 1957 = 20934) starts "counting" at day 1, and interprets the year 1900 as a leap year. As a result, when copying and pasting between different applications (that do not employ the algorithm used in Microsoft Excel, such as Microsoft's SQL Server, which starts "counting" from day 0 and does not interpret 1900 as a leap year), you may see the displayed date changed by two days.
Date values can be displayed in the spreadsheet in numeric format or in one of several predefined date display formats (e.g., 1/6/64, 6-Jan-64, Jan-1964, 01/06/64, 01/06/1964, 6-Jan).
To change the date display format, select Date in the Display format group box of the Variable specifications dialog (accessible by double-clicking on the variable name in the spreadsheet or by selecting Variable Specs from the Data menu) and choose one of the predefined display formats.
When you enter data into a new variable using a format that is recognized as valid in the Display format group box of the Variable specifications dialog (e.g., Time, Date, Currency, etc.), STATISTICA displays the Auto Format Cells dialog. In this dialog, you can either apply the format to the individual cell or to the whole column.
You can create a single date variable from two (month, year or day, month) or three (day, month, year) variables as well as split a single date variable into two or three variables via the Date Operations dialog (accessed by selecting Date Operations from the Data menu).