It it now a leap year?

[Karl Larsen]

Antonio Olivares wrote:
>>  ----- Original Message ----
>> From: Karl Larsen <k5di at zianet.com>
>> To: For users of Fedora <fedora-list at redhat.com>
>> Sent: Wednesday, August 8, 2007 5:07:49 PM
>> Subject: Re: It it now a leap year?
>>
>> Mike - EMAIL IGNORED wrote:
>>> On Thu, 09 Aug 2007 06:02:27 +0930, Tim wrote:
>>>
>>>> Andrew Parker:
>>>>>> For bash the following will display 061 if its currently a leap year,
>>>>>> 060 otherwise
>>>>>>
>>>>>> date -d "$(date +%Y)/03/01" +%j
>>>> Kevin J. Cummings:
>>>>> It doesn't work with dates after 2037/03/01 ....
>>>> Leaving you with thirty years to develop a solution, or spend a few
>>>> minutes pondering whether to bother...  ;-)
>>>>
>>>> But seriously, although some might think you don't need to worry about
>>>> such things, there are programs that will need to do some work using a
>>>> date from the future.  The matter is more urgent than immediately
>>>> obvious.
>>>>
>>> [...]
>>>
>>> My program deals only with the present and the immediate past.
>>> Since in 30 years I hope to celebrate (?) my 98th, it would be
>>> quite interesting to see if the problem still concerns me. :)
>>>
>>> Mike.
>>>
>>>
>>     In a terminal type $cal 2 2008 and you will see February has 29 days 
>> when it is leap year according to Google. Do $cal 2 2007 and you will 
>> see this:
>>
>> [karl at k5di ~]$ cal 2 2007
>>     February 2007
>> Su Mo Tu We Th Fr Sa
>>               1  2  3
>>   4  5  6  7  8  9 10
>> 11 12 13 14 15 16 17
>> 18 19 20 21 22 23 24
>> 25 26 27 28
>>
>> So no leap year in 2007
>>
>>
>> -- 
>>
>>     Karl F. Larsen, AKA K5DI
>>     Linux User
>>     #450462   http://counter.li.org.
>>
>> -- 
> 
> I like your solution Karl.  Not to make less of the other answers provided.  Rick provided a C+ program which is awesome.  I like all the answers.  But Karl's way of looking at it, in a leap year February has 29 days, so check by generating a calendar for the month of February month 2 and the year and if it has 29 days, it is a leap year, if it does not then no leap year.  No need to worry about if the year ends in two zeros, which is divisibe by 100 without a remainder.  If the number of the year ends in a 4,8,12,16,20,24, any multiple of 4, it is a leap year.  There is a rule 
> cal 2 year  where year is a number from 1 to 9999  after that the program does not work.  
> 
> 1700 is a leap year, 1704,1708,1712,1716, ... and so on
> 
> The rule 
> if year modulo 400 is 0 then leap
>  else if year modulo 100 is 0 then no_leap
>  else if year modulo 4 is 0 then leap
>  else no_leap
> where modulo is the remainer when the year  divided by 400 is 0, leap year
>  else if the remainder is zero when the year is divided by a 100, leap year
>     else if the remainder is zero when the year is divided by 4, then leap yaer
>        else no leap year
> 
> [olivares at localhost ~]$ cal --help
> cal: invalid option -- -
> usage: cal [-13smjyV] [[month] year]
> [olivares at localhost ~]$ cal 99999
> cal: illegal year value: use 1-9999
> [olivares at localhost ~]$ cal 2 1700
>    February 1700    
> Su Mo Tu We Th Fr Sa
>              1  2  3
>  4  5  6  7  8  9 10
> 11 12 13 14 15 16 17
> 18 19 20 21 22 23 24
> 25 26 27 28 29
> 
> [olivares at localhost ~]$ cal 2 1704
>    February 1704    
> Su Mo Tu We Th Fr Sa
>        1  2  3  4  5
>  6  7  8  9 10 11 12
> 13 14 15 16 17 18 19
> 20 21 22 23 24 25 26
> 27 28 29
> 
> [olivares at localhost ~]$ cal 2 1708
>    February 1708    
> Su Mo Tu We Th Fr Sa
>  1  2  3  4  5  6  7
>  8  9 10 11 12 13 14
> 15 16 17 18 19 20 21
> 22 23 24 25 26 27 28
> 29
> 
> [olivares at localhost ~]$ cal 2 1712
>    February 1712    
> Su Mo Tu We Th Fr Sa
>                 1  2
>  3  4  5  6  7  8  9
> 10 11 12 13 14 15 16
> 17 18 19 20 21 22 23
> 24 25 26 27 28 29
> 
> [olivares at localhost ~]$
> 
> ..., every 4 years, there is a guaranted leap year!  Unless we die of course, there is no leap year for us.  
> 
> Great solution Karl!  
> 
> Regards,
> 
> Antonio
> 
> 
> 
> 
> 
>        
> ____________________________________________________________________________________
> Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. 
> http://answers.yahoo.com/dir/?link=list&sid=396545433
> 
	glad you like it. The cal program is VERY powerful.


-- 

	Karl F. Larsen, AKA K5DI
	Linux User
	#450462   http://counter.li.org.