date -> text convertion error

I have run into a strange type convertion bug in PostgreSQL.  I have a
table with a 'birtdate' field with type 'date'.  I convert this to
text to reformat it to a string 'DDMMYY'.  A few dates are converted
wrong.  The first example moves the birth date from 25. to 24.:

  pere=> select birthdate, birthdate::text
     from user_appl where fname = 'Antal';
   birthdate|text
  ----------+----------------------
  1965-04-25|1965-04-24 23:00:00+01
  (1 row)

  pere=> select birthdate, birthdate::text
  from user_appl where fname = 'Petter';
   birthdate|text
  ----------+----------------------
  1973-07-11|1973-07-11 00:00:00+01
  (1 row)

  pere=>

What is going on, and how can I stop this from happending?

System Configuration
---------------------
  Architecture (example: Intel Pentium)         : Intel Pentium II
  Operating System (example: Linux 2.0.26 ELF)  : RedHat Linux 5.2 / 6.0
  PostgreSQL version (example: PostgreSQL-6.5)  : PostgreSQL-6.5
  Compiler used (example:  gcc 2.8.0)           : gcc 2.7.2.3
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##>  Petter Reinholdtsen <##    | pere@td.org.uit.no
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