Requirement coverage historical gadget should be configured by the last X days

whenever using the req coverage history gadged in a dashboard or embeded in a wiki page, the configuration of this gadget has a start date and an end date, which are fixed after being saved, making this gadget "useless" in real cases where we want to see evolution in terms of the coverage overview for "last X days".
the req coverage history gadget configuration should be based in the last X days, instead of a start and an end date.