When displaying the Jira issues Calendar, the last days from the previous month are displayed greyed out if you select the current month, as long as they are in the same week that the first days of the current month:

However, the issues related to the days of the previous month are not displayed when selecting the current month, so you must select the previous month to make it visible in the gadget:

It would be great if the issues could be displayed or the greyed out days too, without the need to switch it back to the previous month.