Complex sentence: During the 1999 U summit in Helsinki the country was invited to start membership talks with the Union, currenly almost completed and January 1,2007 has been set as Bulgaria's accession date.
Split into simpler sentences: During the 1999 EU summit in Helsinki, the country was invited to start membership talks with the Union. These are currenly almost completed, and January 1,2007 has been set as Bulgaria's accession date.