arduino web thermostat controlled with android phone

Hi, I state that I am new in the field Arduino, but I come from the old school Atmel. I would chidere one thing. The project I'm testing on an Arduino Uno. I would understand why I get an error compiling this:

Termostato:1108: error: 'class DateTime' has no member named 'dayOfWeek'

if (now.dayOfWeek() == 0 || now.dayOfWeek() == 6) {

^

I would like to figure out how to solve this error. Thanks so much. if you can help ...