ELI5 How can the universe be infinite if it is approx. 13.75 Billion years old?

Using Distance = Speed x Time

Speed of light = 300,000,000 m/s Time = 13,750,000,000 x 365.25 x 24 x 60 x 60 = 4.34x10^17

Therfore radius of universe = 1.30x10^26m or 1.30x10^23Km

not infintie??