Operation Manual

Appendix B: Reference Information 384
Days between Dates
With the dbd( function, you can enter or compute a date within the range Jan. 1, 1950, through Dec.
31, 2049.
Actual/actual day-count method (assumes actual number of days per month and actual number of
days per year):
dbd( (days between dates) = Number of Days II - Number of Days I
Important Things You Need to Know About Your TI-84 Plus C
TI-84 Plus C Results
There may be a number of reasons that your TI-84 Plus C is not displaying the expected results;
however, the most common solutions involve order of operations or mode settings. Your calculator uses
an Equation Operating System™ (EOS™) which evaluates the functions in an expression in the
following order:
1. Functions that precede the argument, such as square root, sin(, or log(
2. Functions that are entered after the argument, such as exponents, factorial, r, ¡, and conversions
3. Powers and roots, such as 2^5, or 5*square root(32)
4. Permutations (nPr) and combinations (nCr)
5. Multiplication, implied multiplication, and division
6. Addition and subtraction
7. Relational functions, such as > or <
8. Logic operator and
9. Logic operators or and xor
Number of Days I = (Y1-YB)  365
+ (number of days MB to M1)
+ DT1
+
Number of Days II = (Y2-YB)  365
+ (number of days MB to M2)
+ DT2
+
where: M1
DT1
Y1
M2
DT2
Y2
MB
DB
YB
=
=
=
=
=
=
=
=
=
month of first date
day of first date
year of first date
month of second date
day of second date
year of second date
base month (January)
base day (1)
base year (first year after leap year)
Y1 YB–
4
------------------------
Y2 YB–
4
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