help p\z ssasas ds

i have the following data:

a = xlsread('outdoorall.xlsx','G2:H52364');
b=xlsread('indoorall.xlsx','G2:H52364'); %2397
time=xlsread('outdoorall.xlsx','G2:G52364');
for i=1:2364
dt=(b(i+1)-b(i)); % change in indoor temperature divided by time
c=dt/a(i)-b(i);
plot(c)
end

the problem is my time periods are irregular so im struggling to code DT above as idk how to set time??? i dont want to use xlsread due to this

i was told to find a function or code it by myself but idk understand matlab very well

also is my for loop correct??