x1 is the birthday of x2 with activities x3; x1 is the annual celebration of x2 growing in age by 1 full year.
Unlike all the other terms for "birthday" which all focus on the date of birth, this focuses on the fact that x2 gets older by a year. See also jbedetri, tejbe, jbedetnunsla, jbenunsla, nanca, banro, nunsla.