**Introduction**

The program DATENO calculates the number of days from January 1. The program prompts whether we are working in a leap year or not.

With D = Day and M = Month, the days between January 1 and any other date within the calendar year is:

If M = 1 and M = 2 Then

DATE# = int(30.6 * M + 368.8) + D – 400

Otherwise,

DATE# = int(30.6 * M + 1.6) +D – 35 (non-leap year)

DATE# = int(30.6 * M + 1.6) + D – 34 (leap year)

**TI-84 Plus Program: DATENO**

“DAYS AFTER JANUARY 1”

“2019-03-07 EWS”

Input “MONTH: “,M

Input “DAY: “,D

Disp “0:NO, 1:YES”

Input “LEAP YEAR? “,L

If M≥3

Then

int(30.6*M+1.6)+D-35+L→T

Else

int(30.6*M+368.8)+D-400→T

End

Disp T

**HP 41C/DM 41L Program: DATENO**

(^T: beginning of an alpha string)

01 LBL^T DATENO

02 ^T MONTH

03 PROMPT

04 STO 01

05 ^T DAY?

06 PROMPT

07 STO 02

08 ^T LEAP? N=0,L=1

09 PROMPT

10 STO 03

11 RCL 01

12 3

13 X<=Y?

14 GTO 00

15 30.6

16 RCL 01

17 *

18 368.8

19 +

20 INT

21 RCL 02

22 +

23 400

24 –

25 GTO 01

26 LBL 00

27 RCL 01

28 30.6

29 *

30 1.6

31 +

32 INT

33 RCL 02

34 +

35 35

36 –

37 RCL 03

38 +

39 LBL 01

40 STO 04

41 END

**Examples**

Days between January 1 and February 16 (M = 2, D = 16): 46

Days between January 1 and October 1 (M = 10, D = 1):

(Non-leap year): 273

(Leap year): 274

Eddie

All original content copyright, © 2011-2019. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.