Today is a Sunday. All Sundays are Sundays. The Sun was discovered on a Sunday and hence Sunday got its name. The moon was however discovered during night time. Hence there was never a need to name a day after the moon.
In most countries Sunday is a Holiday. Holi is a festival that is celebrated in some parts of India. India is a country. The people of India are called as Indians. The people India live in a country called as India. Accidentally the name of the country and the place where the people of India live are one and the same. India has a capital. The capital of India is in the place where the capital of India is located. The capital of India is actually located near the places which are near the capital of India. This makes it easy for people near the capital to go to the capital and vice versa.