It is mentioned in the Qura'n that Allah created the universe in six days, the word" days" means phases or long stretches of time to create the universe, and they are not like the days which humans count because the phrase "your reckoning" isn't mentioned in all the verses which talks about the six days of creation. As Allah said:" And He it is who has created the heavens and the earth in six Days and His Throne was on the water, that He might try you, which of you is the best in deeds. But if you were to say to them ( you shall indeed be raised up after death,) those who disbelieve would be sure to say, (This is nothing but obvious magic) (V. 7 Surah Hud)
(Allah it is He who has created the heavens and the earth, and all that is between them in six Days. Then He rose over (Istawa) the Throne (in a manner that suits His Majesty). You (mankind) have none, besides Him, as a Wali (protector or helper) or an intercessor. Will you not then remember (or receive admonition)? ) (V. 4 As- Sajdah)
The creation of the geological features of the earth, starting from the earth crust hardening until the existence of humans, took 4.5 billion years according to a study made on the earth age. This means that the age of the universe is (4.5×3)=13.5 billion years, and this number is similar to what NASA( National American Space Agency) discovered lately through using space shuttle with high developed equipments to observe the universe, as it estimated the universe age by 13.7 billion years.
Reference : "the universe and the scientific miracles in Qura'n" By Mansur hasab al nabi
Aljazeera site( NASA announces the age of the universe) Wednesday 11/12/1423 12/2/2003 .
Summarized from The Quran Miracles www.55a.net