You can evaluate that statistic on the t(N-p) pdf where N is the length of the time series and p is the number of parameters you are estimating. Keep in mind that for even small time series lengths, this N-p number will exceed 30. If you have a t distribution where the number of degrees of freedom exceeds 30, then you can essentially use the N(0,1) distribtuion.
Compare:
1-tcdf(2,30)
ans =
0.0273
1-normcdf(2,0,1)
ans =
0.0228
So for your T statistic of 1.85, take your time series length - the number of parameters you are estimating and set that equal to dof, then do:
2*(1-tcdf(1.85,dof))
that gives you the significance level.
