No, it's not comfortable for him, that's for sure... his gonads must be huge after all these years of a bad light schedule, poor thing! But there is nothing doing until the days get shorter.
I don't go by the actual sunrise or sunset time, I go by the sky but I've been doing this for so long that I actually wake up as soon as there is any light in the sky and, apparently, keep a subconscious mental 'eye' for the sunset

I also cheat a bit because I don't really change the time of their covering and uncovering every two weeks so, sometimes, I uncover them at the first sign of light and, sometimes, I uncover them when there is already some light -like, right now, I am getting up around 5:20 to uncover them but as the season progresses I get up at 5 am. Same thing with the covering, sometimes I do it when there is still the tiniest bit of light in the sky and sometimes I do it when it's completely dark. It doesn't seem to affect them much, at least not in the sexual hormone production department.