No, we should not fast according to information got on net, phones,etc but fast according to your moon sighted by naked eyes. First of all, we should know that our deen has been completed on the day of Arafah. In the Hajjatul Wada`, the last hajj of the holy prophet SAW, on the Friday, when all sahabas were gathered in Arafah, then this ayah was revealed:’’Today, I have completed your religion.’’(Sourah 5: Verse 3) As such, we should know that technology, worldwide exchange of information instantly, etc would not an already completed deen. Nothing is to be add to that, nor would be substracted. If a time comes that lost all technologies or all fuel got finished and the sun pales up, then there will be no energy to allow us to communicate with each other. We would return to primitive means again. And in fact, there are ahadiths that mentioned that at the end of times, horse would be a means of transport. The well(puit) would again be a source to have water. As such in those times, we will not be able to communicate with each other so quickly, so we would fast according to our moon sighting. Not sooner than 100 years ago, everybody was fasting according to their moon sighting. As technology and information will not change our deen. Furthermore, some advocates that since we have information we should follow the given info. But we find a sahih hadith in Muslim shareef that tells us that sahabas in Madinah ignored the information they received on the moon sighting in Syria. Although Syria was the capital of the Islamic empire, but still all the sahabas of Madinah Munawarah followed the moon sighted in Madinah. Nor was there imposition to follow the moon of Syria. Since the day of Arafah is the 9th Zil Hijjah, then it is incumbent to follow one`s own sighting and not of Saudi. The day the hajees are getting together in Arafat is for them especially. As such, we would fast on the date of 9th of Zil Hijjah in your particular country. Please see for a more detailed answer on the qna ‘’When to fast to Arafah’’.