Is there a way of converting date formats for all date fields in all maps at once? I've noticed that date fields don't seem to inhereit the date formats from the layer itself, so I'm having to change the date format for every layer, in every map.
I found an answer to my problem and rather than deleting my question I thought I'd put the answer here for those to see.
Go to: ArcGIS Online Assistant
Find your content from the search bar at the top of the screen
Click the drop down next to the "I want to.." and click "view JSON".
Click on the map of interest.
Scroll down the JSON file until you get to the data section
Click the pencil to edit the JSON file.
Find and replace "shortDateShortTime" with "shortDateLE" or "shortDateLEShortTime" (to include the time). Click save and repeat for every map.
Retrieving data ...