Sometimes I'm looking for date-sensitive information and don't want to see results more than a certain age. Is there a way to specify this in a Google search?
Yes, you can.
These options appear in the query string. I don't think there is a way to include them in the regular search input as a search operator. In other words, I don't think it can be used like the filetype search term.
Once you preform the Google search, you can click on More search tools and then Custom Range...
This will use the publication date, which Google describes as:
If want to search for pages which contain a date (year only) within a given range, you can use the Numrange search feature. (e.g.