Is it that you do not know your birthday, or you have simply lost track of the time?

[ he's met many people, mostly war orphans like the two of them, who only have a vague idea about how old they are. it's not unusual. ]

[ he squeezes her hand. ] Not because of you. That is what war does to people.

[ he does have a better general idea though, given the records the alliance had of jyn with saw, even if it's not exact dates. ]