indicate period covered in snapshot

[ghost]

as per zendesk ticket #897:

Searches are limited by number of matches not by time. if I understand correctly, a search for a >popular term might only go back an hour where a search for an obscure term might go back days. It >would therefore be handy to indicate prominently the period covered in a given snapshot. Also, it >would be good if the timestamp for the saved snapshot (and if implemented the timestamps covering >the duration) were displayed given the user's own time zone. I saved a search at 10:50 local time in >Toronto and it was reported saved at 15:50.