Because the Muslims do follow the lunar calendar the month of Ramadan will occur.
He said: "Ramadan is the month in which the Quran was revealed as guidance and clarification to humankind, and a distinction between right and wrong. So, whoever from among you witnesses the month should fast it." (2: 185)
So Ramadan is often called the holy month as Muslims try to spend much of their waking hours readingtheir Holy Book.