Get SSMS to show the time a query completed at?
Hitting F4 also enables properties view, which shows the start time, finish time, and run time.



Also, if you Include Client Statistics (under Query menu), you can get a history of when you ran the query, along with various statistics such as run time and number of rows.



Update, 2019-10-14: SSMS 18 now includes the completion time in the Messages pane of the results tab.