A question in response: with whom do Caldari people celebrate their private things?
The closest people my own Caldari characters are to, are those that they served with during their days in their military units and they tend to celebrate in the same ways they did when they were in active service: drinks at an obscure bar in some alleyway near the bases they were stationed at where the bartender still knows their name; a small barbeque joint that only serves locals near the dorms they were trained; or that karaoke place where they can sing out of key and embarrass themselves in each others company.
In Caldari society I feel there's a degree of always having to maintain a social mask, where you don't express what you actually feel, but what you feel is expected of you to express what you feel. That there's a difference in feeling between what would be considered "friends". There's friends that are acquaintances, colleagues, associates, subordinates, or superiors. Then there's your friends that transcend that, and they're the ones you don't wear social masks with because you trust each other implicitly and have earned that over years of shared experience together.
I think there's a danger in thinking that Caldari militarism is just all about marching around a parade ground. It's a powerful social institution that can develop strong social bonds between people who have had to work together, train together, live together and experience both triumph, failure. I don't think the term, "kirjuun" directly translates to, "friend" as we know it but carries with it the connotation of those people you love who have become like a sister or brother to you in the company of being fellow soldiers. Which probably has deep cultural roots in the fact that the Caldari appear to have had a harsh and violent history on their home planet full of feudal conflict, imperialism, and then the rivalry of nation-states controlled by warlords.