The groups that believe in something eschatological are called religious, and are characterized as having one or more holy books, holy gatherings, exegesis of those books in sermons, rituals, containing a form of communion, a form of confession, rituals with light and singing, study groups, etc.
Then I wonder if atheists that are believers of the fact that there is no god, have to be considered as a religious group. They have gatherings in quite exclusive meetings, have testimonials and some kind of sermons, study groups trying to unify the non-belief, etc.
Both "groups" seek togetherness as together they feel stronger.
The more I think of it there are significant differences, but there are also significant similarities. Even as I attend conversation-meetings of such an (mainly) atheistic group, I keep some distance, because I want to cherish my own thinking.

Personally, I feel more comfort by non-religious or agnostic. The "I don't know, because I can't know" feels much better, and the core of my non-belief is that all religions are the same in their actions to group people to their own behalf, their own interests, their own income using magic and fairy-tales . Although I believe that a lot of religious people are sincere, honest and believe because they have been taught that way.