f(x) = a*exp(-b*(x-xo))*cos(w*(x-xo)-t)+c

xo = lower parameter of xrange

fit1 xrange [82700:83200]
fit2 xrange [86350:86750]
fit3 xrange [89730:90220]

time = 0 in data file corresponds to 
Nov. 03, 2004 06:30:09 PM