Solution 34851: Finding Days Between Dates on the TI-83 Plus and TI-84 Plus Family of Graphing Calculators.
How can I find the days between dates using the Finance App on the TI-83 Plus and TI-84 Plus family of graphing calculators?To calculate the number of days between two dates using the actual-day-count method, use the date function dbd( ) or "days between dates". date1 and date2 can be numbers or lists of numbers within the range of the dates on a standard calendar. The dbd( ) function is found by accessing the Finance App and selecting option D.
The syntax is as follows:
Please Note: For the TI-83 Plus, TI-84 Plus, and TI-84 Plus C Silver Edition the dates must be between the years 1950 through 2049.
Additional Note: For the TI-84 Plus CE the dates must be between the years 1980 through 2079 on the latest version of OS.
date1 and date2 can be entered in either of the two formats below:
• MM.DDYY United States
• DDMM.YY Europe
1) Press [APPS]  [ALPHA] [D].
2) Press   [.]     [,].
3) Press   [.]     [)].
4) Press [ENTER].
Please see the TI-83 Plus and TI-84 Plus Family guidebooks for additional information.