Gmail users can now search by date range, message size and exact word match rather than keyword.
For instance, users tired of turning up messages from 2007 in their search results can limit their searches to those less than a year old using “newer_than:1y.”
Gmail adds the new search tools to a number of advanced search methods it already supports.
This is great news for FBI agents investigating nasty emails of the :-< (Broadwell's to Kelley) or °O° (Petraeus's to Broadwell) varieties.
To minimize your chances of having G-men use these search tools against you, check out this EFF email privacy primer.