how can I show the age or number of years for birthdays and anniversaries in the calendar for Thunderbird, Lightning.

I can find no settings to turn on a count for the number of events for recurring events like birthdays and anniversaries. I would like it to show, for instance, John Doe Birthday Oct 11, 2015 age 20 or whatever it is. It seems to be a simple request that is done by most other calendar applications. If you have the DOB, it should be a simple calculation of current year minus year of birth if the birthday has already passed, or current year minus one, minus year of birth if the birthday is still in the future for the calendar year