Often we get asked how to make a rate available only for a specific time period. There are a few ways to do it, depending on which tools you use:
1) If it's a Package Rate (which requires the Packaging Module: http://www.bookingcenter.com/products/modules/packages.html) then there is a 'from:' and 'to:' date field for each Package that would make a Package Rate available for only a specific time period.
2) If it's a normal Rate (i.e., non-Package rate), then using the Closed to Arrival for a Rate can set the time period before and after your desired dates to not allow an arrival, so that it will only display for the dates desired. Thus, if you close the rate for all dates before June 1 and after July 31, then it is effectively available only for June 1 - July 31.
Regardless of which approach you use, the Rate will have to be allocated to the Agent channel in which you wish to make it available (MyPMS Front Desk, website, GDS, etc). See: https://support.bookingcenter.com/index.php?/Knowledgebase/Article/View/205 for assistance with Agent Allocations.