A timer that starts a time cycle when a filter is placed into a housing is disclosed. The timer cycle will not reinitiate a new time cycle when the previously used filter is removed from the housing and reinserted into the housing. In one embodiment, the filter timer assembly includes a filter having a filter media surrounded by a filter frame, a housing for supporting the filter, a piercing post connected to the housing moveable between a first resting position and a second position in direct contact with the filter frame, and a timer connected to the piercing post. The piercing post punctures a portion of the filter frame to create an opening in the filter frame. The timer initiates a count when the piercing post is actuated to the second position.