FFT of data with initial dwell time offset

Hi all,

I have a data set acquired across time (N=32). The data is equally spaced between the first and last points;the spacing between the each point is 9 seconds.

However the first data point is collected at time = 5 seconds. The FFT is conditional on the data samples being evenly spaced, which it is. My question is how do I take into account this initial offset of 5 seconds?

Many thanks, T