Assalam o Aliakum

Ramadan Mubarak in Advance.
Allah tala hum sab ko is maheena ki barkaton se faiz yaad kare aur hamain Ramadan k elawa bi aise hi naiki per chalaye ameen sumameen.

The Arrival of Ramadan

This event is confirmed by sighting the new moon, even if it is seen by only one just person, or by the passage of thirty days in the immediately preceding month of Sha`ban.

Ibn `Umar said: "The people were looking for the new moon and when I reported to the Messenger of Allah that I had seen it, he fasted and ordered the people to fast." (Related Abu Dawud, Al-Hakim, and Ibn Hibban, who declared it to be Authentic.)
Abu Hurairah reported that the Prophet, peace and blessings be upon him, instructed: "Fast after you have seen it [the new crescent] and end the fast [at the end of the month] when you see it. If it is hidden from you, then wait until the thirty days of Sha`ban have passed." (Related by Al-Bukhari and Muslim)