Time when people are relaxing / just got home from work. Maybe 8-10 pm ÂŻ\_(ă)_/ÂŻ depends what time zone you're aiming at too.
As for advertising, promote your comics on every art community and social media you have. ie: dA, FB, IG, Twitter, art/webcomic-relate discord channels, other obscure art forums, tell your friends, co-workers (and tell them to share) etc.