As explained earlier the Sankashtha
Chaturthi becomes Angaarak Chaturthi when the Foruth Day of the moon falls, in the dark half, on the Tuesday. Then the Chaturthi Day has the added significance owing to its falling
on the Tuesday. On this day, strict vow should be observed. Glorifying the merit of the vow, the 'Ganesh Purana' gives an interesting story.
When the sage Bharadwaj got a son from the earth, as red as the flower of 'Jaaruband', he gave him the name 'Bhaum' which literally means (the son) of the earth. When Bhaum came of
age, sage Bharadwaj gave him 'The Ganesh Mantra' and explained the procedure to chant it. Then he asked Bhaum to go to the bank of river Narmada and chant the 'Mantra' observing total
continence and piety of the character. That was the 'Ekakshari Mantra, which Bhaum chanted with total devotion. Seeing that great devotion and concentration of the boy Bhaum,
Lord Ganesh was delighted and appeared before his devotee on Magh Krishna Chaturthi (Fourth Day of the lunar month Magh, i.e. between January and February of the English or Gregorian
Calender in the dark fortnight) and declared that he who does so on Angaarak Chaturthi will have his all enemies destroyed and troubles removed. The Lord also gave the boy Bhaum, the
right to imbibe the nectar churned out from the ocean, thus providing him the goodhood. The Lord also declared that then-ceforth Bhaum, would be known by the name 'Mangal'. "Since
you are the son of the earth and have red complexion, your one name shall be Angaraka." Hence the name Angarak Chaturthi given to the Chaturthi falling on the Tuesdays.