If your data looks like this
data = {{{2014, 11, 1, 1, 1, 0.696}, 21.1056, 248160.},
{{2014, 11, 1, 1, 1, 1.197}, 41.0738, 249216.},
{{2014, 11, 1, 1, 1, 2.197}, 60.0738, 249216.}}
Then this will give the elements where the second index (x value) is in the desired range
Select[data, #[[2]] >= 40 && #[[2]] <= 80 &]
(* {{{2014, 11, 1, 1, 1, 1.197}, 41.0738, 249216.}, {{2014, 11, 1, 1, 1, 2.197}, 60.0738, 249216.}} *)
To get just the timestamp and x value
Most /@ Select[data, #[[2]] >= 40 && #[[2]] <= 80 &]
(* {{{2014, 11, 1, 1, 1, 1.197}, 41.0738}, {{2014, 11, 1, 1, 1, 2.197}, 60.0738}} *)