As the title explains, why do we have specific days to worship specific gods? For example
So is there any reason behind this?
Actually, the days were not dedicated to any particular god, but to particular planets as per jyotishi. Since the astrologers calculated and formulated rules for time keeping, they used celestial objects as their reference. So each day is dedicated to a particular celestial object found in astrology:
Ravi-var (Ravi - Sun)
Soma-var (Soma - Moon)
Mangal-var (Mangal - Mars)
Budha-var (Budha - Mercury)
Guru-var / Brihaspati-var (Guru/Brihaspati - Jupiter)
Shukra-var (Shukra - Venus)
Shani-var (Shani - Saturn)
But later on due to different reasons like a god's appearance, birth day, or as certain events in mythology took place on a specific day, that day was started to be celebrated for that particular god.
For example, it is believed that Hanuman was born on a Tuesday. Hence, that day is dedicated to him. Lord Shiva holds up the moon on his head, hence known as Chandrasekhara. So moonday (Monday) is dedicated to Shiva. Thursday being dedicated to Brihaspati, the guru of gods, Lord Vishnu is worshipped on this day. It is because Lord Vishnu is Brihaspati Himself:
purodhasāṁ ca mukhyaṁ māṁ viddhi pārtha bṛhaspatim [BG - 10.24]
O Partha (Arjuna), know Me as Brihaspati, the chief of all priests.
Similarly, from other folk stories like Santhosi Mata Vrat, certain days like Friday gained prominence for a particular deity or god. But at the end of the day, all days are actually dedicated to a particular planet as per our jyotishi system.
Lord hanuman is worshipped on Tuesday because on this day Hanuman ji applied sindoor all over his body to please Lord Rama. By seeing this Lord Rama becomes extremely happy and blessed Lord Hanuman that whomsoever will worship you on Tuesday his/her wishes will be fulfilled.
The Shiva Purana Vidyeshwara Samhita mentions Lord Shiva creating the seven days of a week and assigning deities to them. It states that in the very first creation the seven days were ordained by the Lord for different reasons:
At the beginning of the first creation, the omniscient, merciful lord Mahādeva created the different week days for the benefit of the entire world.
Lord Mahādeva, the global physician, the omniscient, the panacea of all panaceas, made the first day his own day that bestows good health.
Next he created the day of his Māyā (Illusion) the bestower of prosperity.
Afterwards when the birth of Kumāra was attended with some mishaps he created the day for the sake of surmounting mishaps and idleness.
With a desire to bless the worlds and for their nurture and protection he created the next day dedicated to Viṣṇu, the protector of the worlds.
The next day created by the lord is for the sake of the longevity of the worlds dedicated to the creator of the three worlds, Brahmā, called also Parameṣṭhin, who is the bestower of longevity too. Hence this day too bestows longevity.
The last two days of the week created by the lord are those of Indra and Yama. In the beginning when the lord created Puṇya and Pāpa (Virtue and Sin) for making the three worlds flourish, these deities who preside over them were assigned these two days. The last two days are the bestowers of worldly enjoyments and removers of premature death respectively. The lord made the sun etc. who are His own manifestations and are firmly established in the solar cycle the lords of the different days.
So as per the Shiva Puran, the weekdays are associated with different gods and celestial bodies because of Lord Shiva.
