I've a Muslim friend that let us know when it's Ramadan time, because it's when he stops to drink beer for a while...

There are many Muslims that are perfectly OK.
I don't know about that. That means there is a period of time he stops buying the beer.
(Just kidding)
Actually it was not the period where she had to stop buying beer. But in Islam beer is prohibited. He may be a drinker, maybe he has not been able to quit his habit, but in the Islamic month of Ramadan is a holy month. The month of Ramadan is the month to gather worship. In the month of Ramadhan is a 1 year occasion, so he will stop drinking for a while because it may still be difficult to quit the habit. In the month of Ramadan worship rewards from Allah 2 times, but sin is also doubled if sin. In essence, the month of Ramadan is an important month for Muslims. And Ramadan is 2 weeks away from today.