How to find the day number of any year from a date?

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I am very new in programming and therefore it is probably a novice's question. I have to write a script that takes a number of day(dd), month(mm) and year(yyyy)values arranged in three separate columns of a MATLAB variable and gives the day number of the year(e.g. for 03 March 2012, 31+29+3=63) as output.
  2 Comments
Md. Golam Mostafa
Md. Golam Mostafa on 23 Jul 2015
I have a variable in the workspace containing all the data. Column 1 stores the day(dd), column 2 month (mm) and column 3 year (yyyy). I need to find the day number (for example, for 02/01/2012 day number=2, for 03/03/2012 day number=Jan (31)+ Feb (29)+ Mar (03)=63). The day number is 63. But for 03/03/2013 day number=Jan (31)+ Feb (28)+ Mar (03)=62). I need output of each date in a separate variable.

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Accepted Answer

Peter Perkins
Peter Perkins on 23 Jul 2015
If you are using R2014b or later, the datetime data type allows you to compute the day of year using the day function:
>> x = [2012 1 2; 2012 3 3; 2013 3 3]
x =
2012 1 2
2012 3 3
2013 3 3
>> d = datetime(x)
d =
02-Jan-2012
03-Mar-2012
03-Mar-2013
>> day(d,'dayofyear')
ans =
2
63
62
  2 Comments
Peter Perkins
Peter Perkins on 24 Jul 2015
Presumably, you are not "using R2014b or later". datetime did not exist prior to that.

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More Answers (3)

Andrei Bobrov
Andrei Bobrov on 24 Jul 2015
x = [2012 1 2; 2012 3 3; 2013 3 3];
d = datenum(x);
out = d - datenum(year(d),1,1) + 1;

Jos (10584)
Jos (10584) on 23 Jul 2015
help datenum
and then use simple subtraction

Sergey Kostrukov
Sergey Kostrukov on 12 Feb 2022
Edited: Sergey Kostrukov on 12 Feb 2022
Fractional value of days since biginning of the year (0-364.9999):
daysFrac = days(currentTime - datetime(year(currentTime), 1, 1, TimeZone=currentTime.TimeZone))
To get the whole number starting from 1 (i.e. day index):
floor(daysFrac + 1)

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