The newest addition to the Bones, Christina, has been noticeably absent. However, the tyke will be returning to celebrate her birthday in the 16th episode, set for a Spring air date. As for Christina's age, EP Stephan Nathan promises that trying to make any sense of timeline would be a 'fool's errand'.
“Before viewers start to do the math to determine her exact age and yell at us, please remember the Bones world is not linear and does not proceed week to week as the show does. Trying to determine specific dates and times is a fool’s errand in a fictional world. That said, enjoy the party! Booth and Brennan do.”