snaptime$$ not updated to sysdate

 Hi, I have created a new materialized view at a remote site, A, referencing a base table at site, B. When I insert a record at site A, there's a record in the materialized view log with snaptime$$=01-JAN-4000. Why is the snaptime$$ not updated to the sysdate?
SQL> select * from mlog$_test_mv5;

ID              SNAPTIME$$      D O
--------------- --------------- - -
CHANGE_VECTOR$$
------------------------------------------------------------------------------------------------------------------------
test345         01-JAN-4000       I N
FE
I use the command at site B, exec dbms_mview.refresh(list=>'es_test_mv5_mv', method=>'F', refresh_after_errors=>TRUE);. This does insert a new row at site B, and the record in the materialized view log at site A is deleted after the refresh.