Logic to find the day given the date

naveengonu · New User Joined: 20 May 2006 Posts: 2 Location: Chennai

Hi All,

I checked the programs in our forum and could find the O/P of 'FIND THE DAY OF ANY INPUT DATE" as incorrect. I/P is

1981/05/06 and O/P is thursday. If you think this as yyyy/mm/dd answer is wednesday or if think like yyyy/dd/mm

answer is Friday. I don't want to point the wrong answer I want to share special quick logic (Or) you can call as

trick.

If you think date as CCYY/MM/DD
Step 1) Left round(YY/4) = S1 (result of Step1)
Step 2) YY+s1+DD = S2 (result of Step2)
Step 3) Just take this codes 144025036146 (So code of Jan is 1, feb is 4, Mar 2 ... nov is 4 and dec is 6).
S2 + (Code of MM) = S3 (result of Step3)
Step 4) S4 = Remainder of (S3/7)

Answer: If you get S4 as 1 it is sunday, 2 is monday, 3 tuesday, 4 wednesday, 5 thursday, 6 friday and 0 saturday.

Note1: For Leap year and if Months are Jan and Feb. Substract 1 at the final.

Note2: Above logic is valid for 1900-99. If you want for 1800-99 (Add 2 to final result), 1700-99(Add 4 to final

result) and 1600-99(Add 6 to final result).

So 2000-99 (Add 6), 2100-99 (Add 4), 2200-99(Add 2) and 2300-99(Add 0).

Hint is calendar will same for all 400 years. I hope I confused you all...

Calc for example: 1981/06/16
S1 = Round(81/4) = 20
S2 = 81+20+16 = 117
S3 = 117+5(Code of June) = 122
S4 = Remainder(122/7) = 3 (Tuesday)

Take todays date 2009/07/10

S1 = Round(09/4) = 2
S2 = 2+9+10 = 21
S3 = 21+0(Code of July) = 21
S4 = Remainder(21/7) = 0 (Again as this 2000-99 add 6 then S4 = 0+6) -----> S4 = 6(Friday)

Try this and let me know if it work for you.

shankar.v · Posted: Fri Jul 10, 2009 3:13 pm

Hi naveengonu,

This link might help you.

Thanks,
Shankar

Bill O'Boyle · Posted: Fri Jul 10, 2009 3:19 pm

Click on the following link -

ibmmainframes.com/viewtopic.php?p=191303&highlight=#191303

Regards,

yogeshwar_ade · Active User Joined: 31 Aug 2006 Posts: 103 Location: INDIA

Naveen,

I have tried for 2009/07/16 but it's failing

Step 1) Left round(YY/4) = S1 (result of Step1) = 02
Step 2) YY+s1+DD = S2 (result of Step2) = 27
Step 3) Just take this codes 144025036146 (So code of Jan is 1, feb is 4, Mar 2 ... nov is 4 and dec is 6).
S2 + (Code of MM) = S3 (result of Step3) = 27
Step 4) S4 = Remainder of (S3/7) = 6

As it's 2009 , so adding 6 to it gain which comes to be 12 which is out of your range given.....

Awaiting for your reply.

Bill O'Boyle · Posted: Thu Jul 16, 2009 7:14 pm

Did you click on the above link and try the code provided?

The date needs to be in CCYYMMDD format (no edit characters).

Why reinvent the wheel?

naveengonu · New User Joined: 20 May 2006 Posts: 2 Location: Chennai

Hi Bill,

Your suggestion is very great for me programmatically, I accept this suggestion. I was just sharing this where you can do the calculation in your mind..

Regards
Naveen.G