01042020, 10:30 AM
HP11C Solutions Handbook doesn't provide the Calendar Routines.
Found that HP55 Mathematic programs got the "Calendar Routines" program so
I adapted this program to work for HP11C
For those who have HP55 Mathematic Program book this routine is on page 75
As stated in this book:
This program called March 1, 1700, day 1 and gives every succeeding day a
corresponding number. The program works for days to and including February 28, 2100.
However, for days from
March 1, 1700, to Febuary 28, 1800, 2 days must be added to tha answer and for days from
March 1, 1800, to February 18, 1900, 1 day must be added.

Procedure: [USER] [FIX] 0
[A] Month // 1 for January
[B] Day // 1 to 31
[C] Year // 2020
[D] Day of the Week // 0 = Sunday
[E] Days Between Two Dates // 1st Date start Label [D] 2nd Date [E]

Example:
What day of the week for 1/4/2020
1 [A] display 1
4 [B] display 4
2020 [C] display 2020
[D] display 6 // Answer is Saturday

Dates from previous problem how many days to 1/31/2020
Month and Year is the same only change the day to 31
31 [B] display 31
[E] display 27 // Answer: 27 days

Program:
Gamo 1/4/2020
Found that HP55 Mathematic programs got the "Calendar Routines" program so
I adapted this program to work for HP11C
For those who have HP55 Mathematic Program book this routine is on page 75
As stated in this book:
This program called March 1, 1700, day 1 and gives every succeeding day a
corresponding number. The program works for days to and including February 28, 2100.
However, for days from
March 1, 1700, to Febuary 28, 1800, 2 days must be added to tha answer and for days from
March 1, 1800, to February 18, 1900, 1 day must be added.

Procedure: [USER] [FIX] 0
[A] Month // 1 for January
[B] Day // 1 to 31
[C] Year // 2020
[D] Day of the Week // 0 = Sunday
[E] Days Between Two Dates // 1st Date start Label [D] 2nd Date [E]

Example:
What day of the week for 1/4/2020
1 [A] display 1
4 [B] display 4
2020 [C] display 2020
[D] display 6 // Answer is Saturday

Dates from previous problem how many days to 1/31/2020
Month and Year is the same only change the day to 31
31 [B] display 31
[E] display 27 // Answer: 27 days

Program:
Code:
LBL A // Month
STO 1
RTN

LBL B // Day
STO 2
RTN

LBL C // Year
STO 3
RTN

LBL D // Day of the Week
GSB 0
STO 4
7
÷
ENTER
INT

7
x
RTN

LBL E // Days between Two Dates
GSB 0
RCL 4

RTN

LBL 0 // Calendar Routines
2
RCL 1
X≤Y
GTO 1
1
+
RCL 3
GTO 2

LBL 1
13
+
RCL 3
1


LBL 2
365.25
x
ENTER
INT
X<>Y
Rv
X<>Y
30.6
x
ENTER
INT
X<>Y
Rv
+
RCL 2
+
621049

RTN
Gamo 1/4/2020