If one collects statistic of number of temples of various deities in India, one will find that the maximum percentage of temples are those of Shiva (Destroyer) followed by Vishnu (PALLAN-KARTA or caretaker of creation), with Brahma (Creator) falling way behind with, perhaps, one designated temple at Pushkar. Conclusions, as to why we worship God (because we are afraid, or for personal gains, or because we love HIS creation), is personal choice of readers.
Since 80% of the Indian population consists of Hindus, it is important that people must know what are the astronomical considerations, and any other physical consideration for celebrating a festival on a specific date. After all, Hindus, have absolute faith in their Dharm (religion), and this faith should not be taken for granted. I, personally, will certainly feel cheated, if I was told that a particular festival is being wrongly celebrated on a different date. In this information age, the information provided by authorities, can easily be verified by the general public. All the other religious bodies are doing this, except, of course, Hindu religious bodies.
Here Kumbha(Aquarius in English) represents Shiva and Makara(Capricorn in English) represents Mata Parvati. And there is a reason for this. As per Vedanta Jyotish (remember VJ has an important role in selection of dates for all Hindu festivals), Kumbha(Aquarius in English) is a Rashi farthest away from the Rashi of Sun i.e. Leo (Singh in Sanskrit). Kumbha is represented by an EMPTY earthen pot. The immediate idea that we get is of abject poverty, and since Saturn owns this Rashi, you can add Karma with detachment.
The other rashi, Makar(Capricorn in English), where moon is, is also owned by Saturn. Mars gets exalted status over here, and Mars, we all know gives exaltation results only through renouncement. Mata Parvati, a princess, belonging to a very rich royal family, renounced everything to marry Lord Shiva. She gets represented during Mahashivratri by Capricorn. She knew she was marrying Lord Shiva, and she knew that Lord Shiva had no worldly wealth and may never ever have a cottage of his own.
The marriage of Lord Shiva with Goddess Parvati represents a marriage of a totally non-worldly person (who is not interested in any worldly pleasure and wealth, and who is feared as Destroyer), with a charming, rich princess, who renounces every comfort and wealth for this marriage.
To Read this Post in Hindi : महाशिवरात्रि