# BM3.1 – Using the TIBAII Plus Calcualtor for Dates Chapter 3, Lesson 1

In this lesson students will:

• apply the DBD function on the TIBAII Plus calculator to a given word problem involving dates

## The Days between Dates Function

When working with interest it will often be important to be able to prorate investments and loans. For example, suppose you wanted to pay off a loan today that you were originally planning to pay off at the end of the year. The bank will want to ensure they collect interest on the number of days since the last pay period, so they prorate the loan, or collect an amount that reflects the difference in the amount of time the loan was originally intended for.

For the purpose of our course, we will learn to calculate the number of days between dates using our calculator. This will be known as using the DBD function. Let’s begin by using the calculator to show there are 365 days in one year.

1. To access the DBD function click , then . The button is the secondary function of the 1 button.
2. Now you are in the DBD function sub-menu. You should see DT1= with some numbers representing a date. All dates must be entered in the format mm.ddyy, with two numbers representing the month, day and year. Do not forget your decimal.
3. Let’s enter $1.0101$ then hit the key to save January 1, 2001 as our first date.
4. Use the arrow to get to the DT2= screen and type $1.0102$ along with the key to save January 1, 2002 as our second date.
5. Use the DOWN arrow to get to the DBD= screen. Hit the button to compute the days between the two dates, and hopefully it reads $365$.

Of course, if you ever need to quit this sub-menu, use followed by . This will return you back to computation mode. Let’s spend a few more moments practicing how to use this calculator function; the video below will guide you through two more examples.