calculating the difference between 2 dates

Dear all,

I would like to calculate the difference between the dates say,

20/11/08 and 12/10/2011 in weeks and in months

cheers

Answer 1

[Walter Roberson]

numdays = datenum('12/10/2011') - datenum('20/11/08');

numweeks = numdays / 7;  %and round() or floor() or ceil() as appropriate

numdaysvec = datevec(numdays);
nummonths = numdaysvec(1) * 12 + numdaysvec(2) - 1;

Note that you might have to give datenum() a hint as to whether the first date is the 11th month of 2008 or the 8th month of 2011.

Also, I used a shortcut here of converting the day offset as if it was a date relative to "year 0". MATLAB has weak leap-year routines that believe that "year 0" was a leap year. More accurate would be to datevec() the original dates and do modular arithmetic.

Oh yes, you also need to decide whether dates in the same month count as "0 months" or as "1 month" for your purposes.

[antonet]

Hi Waterson. I get the following message

numdays = datenum('12/10/2011') - datenum('20/11/08');

??? DATENUM failed.

Failed to parse date string.

Error using ==> datevec at 259

20 is too large to be a month.

Any suggestions?

Thanks

[antonet]

i think it should be

numdays = datenum({'02/11/08'},'dd/mm/yy') - datenum({'09/10/11'},'dd/mm/yy')

[Walter Roberson]

Your date '20/11/08' is ambiguous. MATLAB is guessing incorrectly about the format it is in. You should be telling MATLAB the format when you datenum() the string. http://www.mathworks.com/help/techdoc/matlab_prog/bspgcx2-1.html#bsplnu3-2

datenum('20/11/08', 'dd/yy/mm') or datenum('20/11/08', 'dd/mm/yy') as appropriate

[antonet]

Thank you!

Answer 2

[Andy]

there's something better now since 2014 release I believe:

w = between(startRange,endRange,'weeks')

y = between(startRange,endRange,'years')

m = between(startRange,endRange,'months')

[Peter Perkins]

Indeed:

>> between(datetime('20-Nov-2008'),datetime('12-Oct-2011'),{'weeks' 'months'})
ans = 
  calendarDuration
   34mo 3w

[Rosanna]

Hi all I have to compute the occurrence time (days from the starting date) of a large number (eg N=1000) of events, for which I have the Year, Month, Day, Hour, Minute in numerical format (eg 2008, 05, 23, 08, 34). How can I proceed? Thanks Rosanna