every month fasting days for lord shiva

As in puranas

Austerities & Fastings Connected with Shiva’s Worship

Once Parvati asked lord Shiva as to which were the austerities when on being performed by a devotee,

helps him to attain both worldly accomplishments as well as liberation.

Lord Shiva told her about ten austerities connected with his worship and their methods. He said-

"On the eighty day of every month a devotee should worship me by observing a fast for the whole day

and breaking it in the night. But on Kalashtami a devotee must observe the fast for the whole day and

night. He must not have food on that day. On the eleventh day of the dark-lunar month, a devotee must

worship me and observe fast during the day. He should break the fast in the night. But on the eleventh

Ano Bhadraha Kritavayo Yantu Vishwataha (Let noble thoughts come from every side) – Rg Veda

Vishva Dharma ki Jay! (Victory to Universal Dharma!)

day of the bright lunar month, a devotee should observe a fast for the whole period of day and night. On

the thirteenth day of dark-lunar month a devotee must observe fast for the whole period of day and

night, whereas on the thirteenth day of a bright lunar phase he should observe a fast during the day

and break it in the night. A fast observed on Monday should be broken only in the night."