(71B) Days From January 1, Days Between Dates

[Eddie W. Shore]

HP 71B – Day Counts

Number of Days from January 1

D = Day
M = Month
L = Leap Year indicator (1 if the year is a leap year, 0 if it is not)

Code:

Program DAYJAN1 (183 bytes)
10 DESTROY D,M,L,N
12 INPUT “MONTH:”; M
14 INPUT “DAY:”; D
16 INPUT “LEAP? (Y=1,N=0):”; L
20 IF M>2 THEN 28
21 REM M<=2
22 N=IP(30.6*(M+13))+D-429
24 GOTO 32
27 REM M>2
28 N=IP(30.6*(M+1))+D+L-64
32 DISP “# DAYS:”; N

Test 1: January 1 to May 29, non-leap year (L=0). Result: 148
Test 2: January 1 to May 29, leap year (L=1). Result: 149

Days between Dates

M, D, Y: Month, Day, four-digit year

Code:

Program DDAYS (299 bytes)
10 DESTROY M1, M2, D1, D2, Y1, Y2, F1, F2
11 DESTROY F,M,D,Y,N,X,Z
12 INPUT “1: M,D,Y:”; M1, D1, Y1
13 INPUT “2: M,D,Y:”; M2, D2, Y2
15 M=M1 @ D=D1 @ Y=Y1
17 GOSUB 40
19 F1=F
21 M=M2 @ D=D2 @ Y=Y2
23 GOSUB 40
25 F2=F
27 N=F2-F1
29 DISP “# DAYS:”; N
31 STOP
40 IF M>2 THEN X=IP(.4*M+2.3) ELSE X=0
42 IF M>2 THEN Z=Y ELSE Z=Y-1
44 F=365*Y+31*(M-1)+D+IP(Z/4)-X
46 RETURN

Test 1: January 2, 2015 to March 17, 2016 (1,2,2015 to 3,17,2016). Result: 440
Test 2: March 14, 1977 to June 29, 2016 (3,14,1977 to 6,29,2016). Result: 14352