SQL> create table tbl(n number);

Table created.

SQL> create or replace
  2    trigger tbl_bir
  3      before insert
  4      on tbl
  5      for each row
  6      begin
  7          null;
  8  end;
  9  /

Trigger created.

SQL> select to_char(last_ddl_time,'mm/dd/yyyy hh24:mi:ss')
  2    from user_objects
  3    where object_name = 'TBL_BIR'
  4  /

TO_CHAR(LAST_DDL_TI
-------------------
10/13/2016 15:02:48

SQL> alter trigger tbl_bir disable
  2  /

Trigger altered.

SQL> select to_char(last_ddl_time,'mm/dd/yyyy hh24:mi:ss')
  2    from user_objects
  3    where object_name = 'TBL_BIR'
  4  /

TO_CHAR(LAST_DDL_TI
-------------------
10/13/2016 15:04:00

SQL> alter trigger tbl_bir enable
  2  /

Trigger altered.

SQL> select to_char(last_ddl_time,'mm/dd/yyyy hh24:mi:ss')
  2    from user_objects
  3    where object_name = 'TBL_BIR'
  4  /

TO_CHAR(LAST_DDL_TI
-------------------
10/13/2016 15:04:23

SQL>