Why don't my friends at home sleep?

Are my friends at home sleeping?

I think my friends don't sleep because one friend texted me when it was 12:46 PM here and it was 4:46 AM at home. I think my friends should text after 8:00 or 9:00 AM. I think time differences are confusing because my friend texted me at one time, but I get it at a different time. How can 9 AM in Istanbul, Turkey and 9AM on the same day in Maryland, U.S.A. happen at different times? Because Earth spins and the sun rises at different times in different places.