How to manually set date?

I'm visiting New Zealand, including the Chatham islands. I usually set the time manually, but couldn't find a way to manually change the date. Automatic synching has been a disaster, as my watch now says it's yesterday and is also off by 45 minutes since I'm around the edge of a fractional time zone.

  I've gone back to manually setting the time, but it still says it's yesterday, so is there any way to manually set the date?