For another the beep of an i Phone does the job, thanks to a smartphone application called Ramadan Times.
The app sets the fasting times depending on the location of the device.
Muslims use their gadgets in much the same way as everyone else: they text, they use social networks, they buy online.
People are surprised at their smartphones’ capabilities, says Arif Hisam, head of Pak Data, the Pakistani company that created the app.
Islamic hardliners may have issued a slew of against digital technology, including chat programmes (they could lead to flirting) and the use of Koranic verses as ring tones (disrespectful).
But even in poorer Muslim lands adoption is respectable: 26% in Egypt, not much below Germany’s 29%.
More than a third of people in the Middle East now use the internet, slightly above the world average.
Earlier this year, when Hamza Kashgari, a Saudi writer, was deemed a blasphemer by his country’s authorities for a poem, the internet was filled with hate speech against him.