How to find the time indicating that two time-series data start to be different from each other?

Hi All,

I am comparing the lower limb joint angles during normal walking to those during ramp walking. I have data from 12 subjects while each subject has over 15 trials for each movement.

By comparison, I want to figure out when the joint angles during these two movements start to be statistically different.

I would appreciate any suggestions regarding this case.