Make sure we are consistent with format in DS

@PascalPiche came across this bug while displaying the weekday name: The DS formats the weekday with 'N', which uses ISO-8601 (first date of the week is then Monday as in the US, not Sunday).

There were multiple places where a fix could be applied, but the best solutions we found was to apply the fix in the data-source for two reasons:

1. Field ouput won't change, so less risk to break things
2. The xsl template is agnostic to this change since it was doing string matches