Calculating Time Intervals; Calcul Ating Future Or Past Dates - HP -80 Owner's Handbook Manual

Calculating Time Intervals
Another very useful function involves the
IiII
key. It will determine
the number of calendar days between two dates-ranging from January
1, 1900 to December 31 , 2099-and will check for range and logic
errors. An example of the latter might be February 29, 1973 or Feb-
ruary 30th of any year. An erroneous date-whether a logic or range
error will cause the display to blink. The
IiII
key is used in much the
same way as the other function keys except that the following con-
vention must be observed:
Enter the month number. Follow it with a decimal point, followed
by a two-numeral day number, followed by the full year number.
For example:
May 11 , 1973
June 3, 1984
November 9, 2009
would be entered as
would be entered as
would be entered as
5.111973
6.031984
11.092009
Thus, to find the number of days between two dates, simply key in the
first date and press
SAV E . ,
key in the second date and press
1iII.
The
answer, shown in days, is ready for other operations or input to another
problem. For example, to find the exact number of days between De-
cember 10, 1974 and March 14, 1976,
Enter: See Displayed:
12.101974
SAV E .
3.141976
1iII-_
number of days
Calculating Future
or
Past Dates
You can find a future or past date in the range January 1, 1900 to
December 31, 2099- given the number of days-without having to
count knuckles or remember rhymes. (You don't need to worry if the
year entered
is
a leap year; leap year calculations are handled auto-
matically.) Here's how:
(j)
If you want the year number to be displayed, set rounding for
6 decimal places by pressing the gold key and 6 (number
key).
®
Enter the starting date according to the date convention
(above). Press
SAV E ••
@
Enter the number of days (press
CHS
if you're finding a past
date).
o
Press
1iII.
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