SQL> create table dates as
  2    select date'2000-01-01' +level-1 dt
  3         , to_char(level,'00000000000000000') padding
  4    from dual connect by level<=1e4;

Table created.

SQL> create index ix_dates on dates(trunc(dt,'hh24'));

Index created.

SQL> call dbms_stats.gather_table_stats('','dates');

Call completed.

SQL>
SQL> explain plan for select * from dates where dt between :1 and :2;

Explained.

SQL> select * from table(dbms_xplan.display());

PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------------
Plan hash value: 2394932240

-------------------------------------------------------------------------------------------------
| Id  | Operation                            | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                     |          |    25 |   875 |     3   (0)| 00:00:01 |
|*  1 |  FILTER                              |          |       |       |            |          |
|*  2 |   TABLE ACCESS BY INDEX ROWID BATCHED| DATES    |    25 |   875 |     3   (0)| 00:00:01 |
|*  3 |    INDEX RANGE SCAN                  | IX_DATES |    45 |       |     2   (0)| 00:00:01 |
-------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter(TO_DATE(:2)>=TO_DATE(:1))
   2 - filter("DT">=:1 AND "DT"<=:2)
   3 - access(TRUNC(INTERNAL_FUNCTION("DT"),'fmhh24')>=TRUNC(:1,'fmhh24') AND
              TRUNC(INTERNAL_FUNCTION("DT"),'fmhh24')<=TRUNC(:2,'fmhh24'))