Complex sentence: Since 1988, the race has been held on the first Saturday of July closest to the United States' Independence Day and in 1998 became the first restrictor plate/Daytona race to be held at night.
Split into simpler sentences: Since 1988, the race has been held on the first Saturday of July, close to the United States' Independence Day. In 1998, it became the first restrictor plate and Daytona race to be held at night.