Inserting sysdate with default NLS_DATE_FORMAT

Hi Expert,

I'm trying to get my head around how SYSDATE works , my default NLS_DATE_FORMAT is DD-MON-RR

SQL> select value from NLS_SESSION_PARAMETERS where PARAMETER='NLS_DATE_FORMAT';

VALUE

--------------------------------------------------------------------------------

DD-MON-RR

I inserted values with sysdate

SQL>  INSERT INTO t1 VALUES (TRUNC(SYSDATE), SYSDATE);

1 row created.

How Oracle is able to insert SYSDATE with time frame when the default NLS_DATE_FORMAT is DD-MON-RR ??

I tried to insert a value with time-field in it, but it failed with ORA-01830: date format picture ends before converting entire input string.

I was expecting the same error for sysdate as well