Complex sentence: In January 1973 Switzerland left the previously established Bretton Woods system (1944--1973) and adopted a floating currency system which considerably strengthened the Swiss franc in comparison to the since 1945 constantly declining United States dollar.
Split into simpler sentences: In January 1973 Switzerland left the Bretton Woods system (1944--1973) and adopted a floating currency system. This strengthened the Swiss franc in comparison to the United States dollar.