PL/SQL :: Calculating Value On Insert

10g

I have a table that mirrors remote table. Time info on the source table is in milliseconds (lowest value is 1338699905613)

I'd like to have the target table with DATE column as an addition to the source table columns.

I'm wondering what would be the way to calculate DATE value on insert?

The calculation should be from UTC (in milliseconds) into DATE.

The target table is :

test (ID NUMBER(19,0), STARTTIME NUMBER(19,0), RECORD_DATE DATE);

and data comes with insert from source table (mirror in remote db)

insert test (ID, STARTTIME) select id, STARTTIME from test_o