DateAdd +weeks dropping a few days


This one actually got interesting. After a bit of research, here's what
I found:

Starting with 1/1/2005, and adding years (52 weeks at a time), I get
the following results:

1 Week: 12/31/2005 -0 days
2 Weeks: 12/30/2006 -1 days
3 Weeks: 12/29/2007 -2 days
4 Weeks: 12/27/2008 -4 days
5 Weeks: 12/26/2009 -5 days
6 Weeks: 12/25/2010 -6 days
7 Weeks: 12/24/2011 -7 days
8 Weeks: 12/22/2012 -9 days
9 Weeks: 12/21/2013 -10 days
10 Weeks: 12/20/2014 -11 days


I think what happens is that I loose one day PER YEAR because I add the
year, but not the extra DAY to bump me over to the next year. Then you
notice that I lose an EXTRA day in 2008 and 2012. Both leap years. SO
leap years are partially at the root. How bout that?

Finally, 2014 IS a leap year, but nothing odd happens because we don't
get to it. My test date is january 1.

In the end, I needed to take the results from DateAdd() and add one day
for each year spanned, but also one day for each leap year encountered
in the date range.

B.





Rick B Wrote:
> I could be wrong, but this seems to work for me.
>
> item one (adding 52 weeks) results in the same day next year (minus 1)
>
> item two (adding 104 weeks) results in the same day next year (minus
> 1),
> then the same day the following year (minus1) Result= same day two
> years
> from now (minus2).
>
> In short, you are adding 364 days for every 52 weeks.
>
> 52 weeks loses one day
> 105 weeks loses two days
> 157 weeks loses three days
> etc.
>
> I could be wrong, but this seems to make perfect sense to me.
> Mathmatically, at least.
>
> Now, It is odd that adding 52 weeks results in a different date than
> adding
> one year. I never thought about the fact that a year is actually 52
> weeks
> and one day!
>
> Rick B
>


--
Robert Zeurunkl
.

Relevant Pages

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