Loading and Caching Time-based Data

I'm looking for a good way of caching event entries from a big database so that it's not necessary to load the whole database but only timeframes which contain entries which are currently displayed, selected or otherwise needed. Are there classes in Cocoa or Objective-C programming pattern which provide support to impl开发者_如何学JAVAement this?

I have a property database which pulls down list of available properties for sale. The easiest way I found to do this, was to have a date attribute which gets set when the data is first populated. From then on, only the objects which have a time that's expired are updated when someone attempts to view a property. This was the easiest way I found to control the outcome.