Monitoring with pg_controldata

I am trying to monitor my replication lag with pg_controldata and it's
driving me nuts.

If I run pg_controldata from the command line as user postgres or root
I get the following line

Time of latest checkpoint: Thu 30 Jul 2009 00:36:12 NZST

If I run it from the crontab I get this output

Time of latest checkpoint: Wed Jul 29 23:05:34 2009

Here is the cron entity

/usr/lib/postgresql/8.3/bin/pg_controldata
/var/lib/postgresql/8.3/main >> /tmp/pg_standby_log

What is the issue here? Some sort of a timezone problem? How do I tell
it what time zone to use?

Thanks.