Conversation so far:
what is the importance of ramadan in Islam
Ramadan is the most sacred month of the year in Islamic culture.
when was Ramadan established
Ramadan was established in the 7th century when the Quran was revealed to the Prophet Muhammad. His revelation began in 610 CE in Mecca at Hira Cave on Mount Nur.
when is Ramadan scheduled for in 2020
Ramadan for the year 2020 starts on the evening of Thursday, April 23rd lasting 30 days and ending at sundown on Saturday, May 23.
when did Ramadan begin and end in 2019
Ramadan 2019 started on Monday, 6th May 2019 and ended on Tuesday, 4th June 2019.

Question: how is the date determined each year
Self-contained rewrite: how is the date for Ramadan determined each year