Partial or incomplete dates

Hello all,
this is my first posting to this list. I have been using MySQL for a few
years with a web application for displaying my genealogy database, a
FoxPro database from The Master Genealogist from which I'm dumping a
subset with a Perl script and the DBD::XBase module. I'm now in the
process of developing my own genealogy program, and I have been
absolutely thrilled by the prospect of using PostgreSQL for this
venture.

My first stumbling block is this: How do I store incomplete or partial
dates in PostgreSQL? I ran a Google search on 'postgresql "partial
dates"' and came up with this thread as the only significant match:
<url:http://archives.postgresql.org/pgsql-general/2003-01/msg00888.php>

In MySQL, the checking on dates is very relaxed, so it's totally legal
to enter a date as '1731-00-00', and let your own program logic decide
that this means just the year 1731. Do I have to make my own data type
to store and manipulate partial dates, or has somebody already done it?
Or is there a way to use relaxed date checking in PostgreSQL?
--
Leif Biberg Kristensen
http://solumslekt.org/