1. On the activity stream gadget timestamp for the activity is not shown, instead it shows as for example 30 minutes ago. If we hover over with the mouse on the area it will show the actual timestamp but it's not much user friendly way. Jira Admins should have ability to configure the gadget to show the date/time values using standard format used by look and feel settings.
2. On the service desk project SLA dates are always shown within days,hours, weeks etc. It can be helpful if we have project specific settings to show the actual date/time values in standard dd/mm/yyyy HH:mm or mm/dd/yyyy HH:mm format. Not all project owners find the default format for showing SLA dates useful and may prefer configuring it differently for their project.

As far as i researched we can force Jira to use a specific date/time format globally  by updating the config file on the server but this becomes global and will even affect the project which don't want to use this format. So it makes sense to give ability to configure specific date time format per project or Gadget.