Inverse FFT Time Scale----->HELP

Hi all,

I am doing an inverst Fourier Transform in Matlab and wanted to know how to get the correct time scale for my axis.
If I have 201 data points in the F domain and do an IFFT using 512 points, how do I calculate the timescale? Does anyone have Matlab code for this?

Also, if Nfft is different from npts, I get a complex result. Should I just use the real part of that ifft?

ie:
H is 201 points long.
h = ifft(H,512) -->returns complex vector 512 points long

is the correct usage to do this:
h = real(ifft(H,512));

and how do I calculate the time scale for that?

Thanks
Kyle