Haryali Teej festival is celebrated on tritia i.e third day in shukl paksh of Shravan month of hindu calander. (Shravan month is fifth month of Hindu calendar which comes in August)
Haryali Teej is primarily a festival of ladies. During shravan, greenery spreads all over due monsoon. After hot summer, the weather becomes very pleasant and brings joy and festive spirit. Ladies of all ages gather in group and enjoy the festive spirit by swinging on the swings and singing songs. They decorate hands with henna (mehandi) with beautiful designs.
In Rajasthan, eastern UP and other northern states of India, gifts, sweets etc called Sindhara are sent by in-laws to their daughters.
It is said that on this day Mother Parvati had met Lord Shiva after hundreds of years of sadhana.  It is also said that Mother Parvati had born 107 times to get Lord Shiva in her husband’s form, yet the mother could not receive Shiva in the form of a husband. 108th time when Mother Parvati took birth, then the Shukla side of the month of Shravan would be encouraged in the form of Lord Shiva’s husband.  From then on this fast started. On this occasion, the ladies who worship the Shiva-Parvati, who are happy with sixteen gold, their honeymoon remains for a long period.  At the behest of Goddess Parvati, Shiva blesses that whatever the virgin girl will keep this fast and Shiva will worship Parvati, the barriers to her marriage will be overcome, along with the help of suitable ward. Suhagan women will get good luck with this fast and will enjoy the pleasure of married life for a long time with husband. Therefore, both virgin and Suhagan keep this fast.