Original: Later that day, the storm intensified rapidly, and by 5 p.m. EDT (2100 UTC), Ivan became a Category 3 hurricane with winds of 125 mph (201 km\/h). The National Hurricane Center said that the rapid strengthening of Ivan on September 5 was unprecedented at such a low latitude in the Atlantic basin.
Simplified: Ivan strengthened fast and by the end of the day on September 5 it became a category 3 hurricane.