ArcGIS Online should allow for dates to be stored in hosted services as ISO 8601 (YYYY-MM-DDThh:mm:ssTZD) so that the AGOL front end correctly displays dates as they are recorded. It is silly to make users recalculate their date fields to account for timezones before publishing because the AGOL databases dont store timezone data. Having the time zone data stored with the date makes the calculation converting the presented date into local time no more difficult for the software.
There is a similar idea here.
