When Configuring Dashboards there are relatively few predefined Time Ranges that you can choose. There is an option to create custom time ranges, but when you create a custom time range it is static. The predefined time ranges are all relative to the current time.
Request 1: Allow administrators to modify (add/remove/edit) predefined "Relative" time ranges
Request 2: If for some reason Request 1 poses significant obstacles, can you add predefined time ranges for "last 8 hours" and "last 12 hours"