Complex sentence: Since the 2006 trials none of the main Dutch networks made the move to HD until the summer of 2008 when from June 1 until August 24,2008 the Netherlands Public Broadcasting (NPO) made their primary channel, Nederland 1 temporary available in HD.
Split into simpler sentences: Since the 2006 trials none of the main Dutch networks made the move to HD. This changed in the summer of 2008 when from June 1,2008 until August 24,2008 the Netherlands Public Broadcasting (NPO) organisations made their primary channel, Nederland 1 temporary available in HD.