"important festival" is correct and usable in written English.
For example, you might write, "The annual harvest festival is an important festival in our town."
Diwali is also an important festival in Jainism.
For Shvetambaras, the single most important festival, Paryushana, occurs in the month of Bhadrapada (August September).
Carnival, the most important festival, is held during the week preceding Lent.
Dong Zhi, the "arrival of winter," is an important festival in China.
"Samhain is the most important festival in the pagan calendar," says Starza.
November Bom Om Tuk is the most important festival in the Khmer calendar, celebrating the end of the wet season.
He thus organized two important festivals, Ganesh in 1893 and Shivaji in 1895.
"We've played a lot of big, important festivals, our sets have got great reviews.
"On the contrary," he said, "we consider the dance festival is one of our four most important festivals.
Shichi-go-san, (Japanese: "Seven-Five-Three"), one of the most important festivals for Japanese children, observed annually on November 15.
Hindus celebrate a number of other important festivals, including Diwali, in which all classes of society participate.
