BUG #11883: Year 1500 not treated as leap year when it was a leap year

The following bug has been logged on the website:

Bug reference:      11883
Logged by:          Bruce Hunsaker
Email address:      hunsakerbn@familysearch.org
PostgreSQL version: 9.3.5
Operating system:   Linux
Description:

Entering historical dates we found we could not enter a date of '1500-02-29'
Even though 1500 is documented to be a leap year. Tested with date and
timestamp column types.

To reproduce:
 psql> create table date_test (mydate date);
CREATE TABLE
psql> insert into date_test values ('1500-02-29');
ERROR:  date/time field value out of range: "1500-02-29"
LINE 1: insert into date_test values ('1500-02-29');

psql> insert into date_test values ('1500-02-28');
INSERT 0 1;

So, Feb 29, is not allowed but Feb 28 is.