Date values are different

Hello, I have values for the dates given in LB21B.
I used the code egen LB21B_12=convertCMC(LB21B)
when I apply %td on both values, none of its showing the correct date and both of them are different form each other as well. The right years would be somewhere beteen 2000 and 2005, but here some times it goes back to 1900, or 1959 or forward even 3033.
How do I correct this?
Im using Stata 14 MP.

Code:

Code:

* Example generated by -dataex-. To install: ssc install dataex
clear
input long(LB21B LB21B_12)
180605       .
180605       .
140103       .
140103       .
140103       .
140103       .
140103       .
140103       .
140103       .
 10100  285474
 10100  285481
300903       .
300903       .
     0       .
     0       .
150802       .
150802       .
150802       .
150802       .
150802       .
     0       .
     0       .
     0       .
     0       .
280604       .
     0       .
     0       .
     0       .
     0       .
     0       .
 70600 2126902
 70600 2126905
260604       .
260604       .
260604       .
260604       .
260604       .
261002       .
120604       .
120604       .
120604       .
131101       .
290203       .
290203       .
270802       .
270802       .
270802       .
     0       .
     0       .
170604       .
170604       .
 10301  291601
 10301  291602
 10301  291595
 90903 2744870
 90903 2744865
 90903 2744869
121001       .
250505       .
250505       .
250505       .
280103       .
280103       .
220302       .
240604       .
240604       .
240604       .
 51102 1533454
 51102 1533445
 50103 1503054
 10702  303815
 10702  303803
 10702  303806
 10702  303806
 10702  303810
 10702  303805
 10702  303805
 10702  303806
301103       .
301103       .
 50404 1512210
200700       .
 51002 1530403
120304       .
120504       .
120504       .
130503       .
130304       .
130304       .
110603       .
110603       .
171203       .
171203       .
180902       .
180902       .
 91102 2750919
 91102 2750933
250603       .
250603       .
 21203  623438
end
format %td LB21B
format %td LB21B_12