Have you ever wanted to just search for an email in Classic Gmail or Inbox by Gmail that you know the time frame from which it was received, sometime in December 2013? You don't know the exact date, but you know the range? You could take the hard way and go into the All Mail label (Classic Gmail) or the Done Bundle (Inbox by Gmail) and go one by one.
Or you can use this neat little trick using the search box. This works in both Classic Gmail and Inbox by Gmail, and best of all it works in the Mobile versions as well.
Just type the following in your search box, and BAM, you have your narrowed down list of all emails during the month of December 2013.
You can modify the timeframe to be any range you want, but it is important to note, it must be in the date format YYYY/MM/DD. You can even narrow it down by sender if you would like by adding "from: firstname.lastname@example.org"
There are even more ways you can narrow this search down by using "subject: xxxxx" or "has: attachment" and many many more.
For more ways you can search and filter using Classic Gmail and Inbox by Gmail take a look at the Gmail Search Help Page.