Calculate difference between several variables

[OlsabeckT29]

Hello, I am trying to calculate the difference between the data observed in 2023 and 2024 by month.  I have a total of 84 observations and need to calculate the difference between all 12 months. Below is a sample of how the data is formatted. 

data Have;
    input id 23Jan 23Feb 23Mar 24Jan 24Feb 24Mar;
      datalines;
1 0.54 0.54 0.52 0.62 0.61 0.60
2 0.48 0.45 0.48 0.71 0.68 0.67
3 0.59 0.61 0.59 0.57 0.54 0.58
4 0.61 0.62 0.59 0.62 0.61 0.54
;

 I want a dataset that contains the difference for each month for all 84 observations.

Data Want;
ID JanDiff FebDiff MarDiff
1
2
3
4

I know I can write out all 12 calculations but is their a more efficient coding strategy to calculate the differences?

Thanks in advance

[data_null__]

Several variables suggest an array might be useful.

data Have;
   input id Y23Jan Y23Feb Y23Mar Y24Jan Y24Feb Y24Mar;
   Array _23 Y23:;
   array _24 Y24:;
   array _df Dif1-Dif3;
   do over _23;
      _df = _24-_23;
      end;
   datalines;
1 0.54 0.54 0.52 0.62 0.61 0.60
2 0.48 0.45 0.48 0.71 0.68 0.67
3 0.59 0.61 0.59 0.57 0.54 0.58
4 0.61 0.62 0.59 0.62 0.61 0.54
;;;;
   run;
proc print;
   run;

[PaigeMiller]

Are there ever more than two years for January? Are there ever more than two years for other months? What would we do then?

[OlsabeckT29]

No, we are only looking at the difference between two years.