RE: Leap Year

[Neil Palmer <npalmer@xxxxxxxxxxx>]

Well, 1700, 1800 & 1900 were not leap years. 2000 is.
        Your new calc won't work.  Try for 1900.

        Divide CCYY by 400
                        1900 not divisible by 400

        If divisible then it is a leap year, else
        Divide CCYY by 4
        If divisible then it is a leap year, else it is not a leap year.
                        1900 is divisible by 4, but it's not a leap
year.

A subroutine from an old RPG program I just exhumed.
There is another rule that says that if the year is also divisible
evenly by 4000 (or 3600 - depending on where you find the information)
then it's not a leap year.  It's referred to as a COMMON year - I wonder
what city the conference will be in ?  :-).  
Frankly I don't give a rat's a** what happens in the year 4000 (or
3600).  I'm pretty sure we can assume that none of our programs will be
running at that point !   
(Note that this is fine for dates AFTER the Gregorian calendar
reformation in 1752.  For example, the years 1300, 1400, 1500 and 1700
were leap years).

C           LEAPYR    BEGSR                           LEAP YEAR TEST
C**  Leap Year: If the year is divisible by 4 it is, but if it's    
C**   divisible by 100 it's not, unless it's also divisible by 400. 
C**   We're ignoring the "if it's divisible by 4000 (or 3600 ?)     
C**   then it's not a leap year" rule.   :-)                        
C           FOUR      DIV  4         RES     40        LEAP YEAR    
C                     MVR            MVR4    40                     
C           FOUR      DIV  100       RES               NOT LEAP YEAR
C                     MVR            MVR100  40                     
C           FOUR      DIV  400       RES               LEAP YEAR    
C                     MVR            MVR400  40                     
C           MVR4      IFEQ *ZERO                       Div by 4     
C           MVR100    ANDNE*ZERO                        & not by 100
C           MVR400    OREQ *ZERO                       or Div by 400
C                     MOVE *ON       *IN31             LEAP YEAR    
C                     ELSE                              else        
C                     MOVE *OFF      *IN31             NOT LEAP YEAR
C                     ENDIF                                         
C                     ENDSR                                         


Also a couple of references:
http://www.digtl.com/leapyr.htm
http://wwwcn.cern.ch/~mcnab/n/Cal/README.cal.txt


Neil Palmer                                AS/400~~~~~      
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> -----Original Message-----
> From: VENU YAMAJALA [SMTP:venu_yamajala@goodyear.com]
> Sent: Wednesday, August 26, 1998 12:21 PM
> To:   MIDRANGE-L@midrange.com
> Subject:      Leap Year
> 
> Hi All,
> 
>  I want to know the fool-proof method of determining the leap year
> technique. My earlier logic was :
> 
> Divide CCYY by 400.
> If divisible then it is leap year, else
> Divide CCYY by 100.
> If divisible then it is leap year, else
> Divide CCYY by 4.
> If divisible, then it is leap year, else it is not a leap year.
> 
> But this is not working for years 1900, 1800, 1700, 2100...etc.
> Sometime back
> someone in a meeting pointed out that though 1900...etc are divisible
> by 100, 4
> they are not leap years!!! I heard someone saying that for every 400
> turns of
> the century (means years with 1600, 2000, 2400...etc), they are leap
> years and
> all other 100s are not (1900, 1800..etc). With this variation in mind,
> I am
> coming out with a new algorithm that says :
> 
> Divide CCYY by 400.
> If divisible then it is a leap year, else
> Divide CCYY by 4
> If divisible then it is a leap year, else it is not a leap year.
> 
>  I want to know from the list, whether this new variation is the
> fool-proof technique. If not, I would like to know the one.
> Thanx in advance for any suggestions.
> 
> Rgds
> Vg
> 
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