Below is an image showing you where to find this feature. Enter search criteria into the Omnibox (address field at the top of any web browser) or from wherever you Google things. At the top middle of the Google results page there will be a Tools button. Once you select that, two new menus will appear on the left: Any time and All results. Select Any time and the drop down box will reveal your options within the last year. Select Custom range... and a calendar will appear for you to select the exact start and end dates.