Why the hell should we adopt their time? Near as I can tell, they still think it’s 600 AD. They can’t even get a calendar to work right.
Actually, and I think this is generous, but the book “The Rise of Modern Science: Islam, China and the West” credits Islamic societies as developing nearly on par with other cultures until about 1200 AD.
The author did say that they significantly slowed their pace of development prior to this.
The reason is that it is considered apostasy to pursue studies (theology, law, science) outside of the ideas in the Koran because it is “complete and perfect work”.