Oracle PL/SQL/Date Timezone/Day Calculation

Calculating the number of days of summer in June, Last_Date function

SQL>
SQL>
SQL> -- Calculating the number of days of summer in June.
SQL> SELECT LAST_DAY("20-JUN-97") "Last_Day", LAST_DAY("20-JUN-97") - TO_DATE("20-JUN-97") "Days_Summer" from DUAL;
Last_Day  Days_Summer
--------- -----------
30-JUN-97          10
SQL>
SQL>