A USK Date Hint is a special file that is inserted together with Updatable Subspace Keys to allow clients to locate new (or newer) editions of a freesite.

To allow locating newer editions even after years of updating a freesite, four additional files are inserted:

SSK@<key>/<sitename>-DATEHINT-<year>
SSK@<key>/<sitename>-DATEHINT-<year>-WEEK-<week>
SSK@<key>/<sitename>-DATEHINT-<year>-<month>
SSK@<key>/<sitename>-DATEHINT-<year>-<month>-<day>

The content of these files is rather minimalistic:

    HINT
    45
    2013-7-5

When a USK key is requested, requests for these files (supplied with the current date) are started as well, in order to find the most recent edition without having to download potentially dozens or hundreds of new editions.