Adapted this to an Xlate TCL Fragment to calculate whole years of age. Thanks for Posts.
regsub — {(d{8})(d*)} $xlateInVals {1 2} dob
set age_years [expr ([clock seconds]/(24*60*60)-[clock scan $dob]/(24*60*60))/365.25]
set xlateOutVals [expr {int($age_years)}]
echo Patient age is $xlateOutVals years.