Timezone dates are completely screwy in calendar

When my timezone was set to Sydney, Australia postings that I made in February appear in March on the calendar e.g. posted Feb 28, but calendar displays as posted March 28 eventhough it hasn't arrived yet!! I reset my timezone to GMT again and all the dates were correct again. I thought I should mention this as most antvillers are in european time zone. I'll leave it a few days before I go back to Aussie time btw, datestamps are still wrong too. Regards John