MATLAB: Explaining the output of datevec

datenum

HI all,
I have the following code
   numdays = datenum({'02/11/08'},'dd/mm/yy') - datenum({'09/10/11'},'dd/mm/yy')   
   numweeks28 = numdays / (7*4)
   numweeks28vec = datevec(numweeks28)
that produces numdays =
       -1071
numweeks28 =
-38.2500
numweek28svec =
    -1    11    22    18     0     0
It is not clear to m e what -1 11 22 18 0 0 of numweek28svec means? For example, what is -1,11,…?
Thanks

Best Answer

The 4th line of datevec() syntax is:
[Y, M, D, H, MN, S] = datevec(...)
Where it's self-explanatory that
-1    11    22    18     0     0
 Y     M     D     H    MN     S
Now, the fact that you're doing SomeDate - DateInFuture, determines the negative sign.
Thus,
datevec(-38.25)
says which Year, Month, etc.. is that serial date.
For intuition, supose you are 3 days Before Christ. Datevec would say you're in the Year before BC (thus -1), in the 12th month, 22nd day etc... (assuming he was born the 25th Dec).
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