Unevenly spaced data interpolation

Hi

I want to interpolate sinusoidal data, say sin(t) corresponding to a
time series 't': [T1 T2 T3 2*T1  2*T2  2*T3  3*T1 3*T2 3*T3...]
to get data at [T2-t  2*T2-t  3*T2-t...]. How can I interpolate given
signal? I read about several methods like Savitzky Golay filter etc. I
couldnt implement it. Can anybody suggest me something?

Thanks