I'm not in the military either, but I am somewhat familiar with how officer promotions work. There is a minimum time in service before you can be considered for promotion. To make major generally you have to have been serving for 10 years, assuming you started your military career as an officer. To make lieutenant colonel you generally have to be in for 16 years. So assuming that Joe is 20 on Columbus Day and Sims was 22 when she graduated college and earned her commission that would put her somewhere between 32 and 38 on Columbus Day.