How do I change the date format in iOS?
The time and date format can be set according to the generally accepted usage in a particular region in iOS devices. 

Regions are selected in Settings&gt;General&gt;International&gt;Region Format.



Sorry I misunderstood the question, I'm adding in the following more details.

Independently from the region you can always set the 24-hour time format in: Settings&gt;General&gt;Date &amp; Time&gt;24-Hour Time, the temperature scale in Weather options and the distance scale in: Settings&gt;Maps. 

Anyway, as far as I know, you can't set date format and/or currency, in a different way from the specified region.