R help - May 2010 - Question about difftime()

Dear R experts,

I have a question about the result of difftime() function: Does it
take into account the different number of days in each month. In my
example, I have the following:
> firstDay
[1] "2010-02-20"
> lastDay
[1] "2010-05-20 16:00:00"
> difftime(lastDay,firstDay,units='days')
Time difference of 89.625 days
>
When I count the days I get 88 days from 20/02/2010 to 20/05/2010
consequently the difference in days should be 87.

On the contrary, difftime gives a higher number, so I doubt whether it
takes into account the fact that february has 28 days (or 29). Could
you please help?

Thank you very much in advance.

Kind regards,
Stella

--
Stella Pachidi
Master in Business Informatics student
Utrecht University

On May 20, 2010, at 11:08 AM, Stella Pachidi wrote:
> Dear R experts,
> 
> I have a question about the result of difftime() function: Does it
> take into account the different number of days in each month. In my
> example, I have the following:
> 
>> firstDay
> [1] "2010-02-20"
>> lastDay
> [1] "2010-05-20 16:00:00"
>> difftime(lastDay,firstDay,units='days')
> Time difference of 89.625 days
>> 
> 
> When I count the days I get 88 days from 20/02/2010 to 20/05/2010
> consequently the difference in days should be 87.
> 
> On the contrary, difftime gives a higher number, so I doubt whether it
> takes into account the fact that february has 28 days (or 29). Could
> you please help?
> 
> Thank you very much in advance.
> 
> Kind regards,
> Stella

Try recounting:

8 days remaining in February this year (not a leap year), after the 20th.
31 days in March
30 days in April
20 days in May

Total?  

HTH,

Marc Schwartz