I need some help for the standard error and 95% confidence interval. My understanding is that the 95% confidence interval should be the estimate +/- (1.96 x Standard Error). However, when I ran the following codes, the reported 95% confidence interval is quite different (see attachment regression results). Can anyone help explain why Stata gave me such results? Thank you very much.

Code:
clear
input float prod_x byte(year month)
5.2 1 1
5.4 1 2
6.3 2 1
6.5 2 2
end
 

regress prod_x i.year
Array