Ganesha Chaturthi commemorates the birthday of Lord Ganesh. On this day, beautiful handcrafted idols of the Lord are installed both in homes and in public. Prana Pratishtha is performed to invoke the power of the deity into the idol, followed by a 16 step ritual known as Shodashopachara Puja. During the ritual, various offerings including sweets, coconuts, and flowers are made to the idol. The ritual should be performed at an auspicious time around midday, known as Madhyahna when Lord Ganesh is believed to have been born.
It's important, according to tradition, not to look at the moon during certain times on Ganesh Chaturthi. If a person sees the moon, they'll be cursed with accusations of theft and dishonored by society unless they chant a certain mantra.
Apparently, this came about after Lord Krishna was falsely accused of stealing a valuable jewel. Sage Narada said that Krishna must've seen the moon on Bhadrapada Shukla Chaturthi and was cursed because of it. Furthermore, anyone who saw the moon then would be cursed in a similar way.
The idols of Lord Ganesh are worshiped every day, with an aarti in the evening. The largest Ganesh statues, on display to the public, are usually taken out and immersed in water on Anant Chaturdasi. However, many people who keep an idol in their homes carry out the immersion much before this.
Date: In 2023, Ganesh Chaturthi is on September 19.