I do it by performing the search I want, then when the results come up, there is a “Tools” menu. Clicking that brings up a timeframe dropdown (which defaults to “Any Time”). Then you can select “Past Year”.
On my phone, I have to drag the menu over (touch where it says “All” and “Images”, and drag to the left) to be able to see it. It will be the rightmost choice, “Search Tools”.
I think that specifying the tbs parameter automatically sets the toolbar to the “open” state on the results page automatically. (My guess is that “tbs” stands for “tool bar state”)
This url searches for “trout” as if we had done all of the steps without all the fru fru.
The part of URL after the “?” is called the query string. In this case it is “q=trout”, which means “set the q parameter to ‘trout’”. “q” is the name of the “what to search for” parameter. So the URL is a one-step search for “trout”.
The character “&” is a separator, so the query string has two parts “q=trout”, which as before says “search for trout”, and “tbs=qdr:y”, which apparently means “only show results for the past year”.