These newsletters have always been hard to create as regular web HTML is not properly read by web email interfaces and email clients. I thought that the simplest solution would be to use a web page that would serve as a web version of the newsletter and turn it somehow into newsletter HTML.
Following on from international dates, I also wanted times in the local timezone and format. This was a little more tricky but I think I've got a solution. This is only really appropriate if you have an international app.