chirp function, time array

Hi, In the "chirp" function y = chirp(t,f0,t1,f1, 'linear'), 't' is the time array. Whenever time 't' is not starting from zero the output signal is getting distorted. What is the reason behind that ? How to avoid this scenario ? say t = 2:0.001:5

[Amal George M]

Could you please elaborate on the observed distortion and share the values of other input variables which resulted in this particular observation?