Important if you are coordinating with family in India:
Hartalika Teej falls on September 10, 2029 in Edison NJ, but on September 11, 2029 in India.
Hindu observances are tied to the tithi at your local sunrise (or to a local moment such as sunset or midnight),
so the calendar date legitimately shifts by a day across time zones. Both are correct for their own location.
What Hartalika Teej means
Religious significance
The most austere of the Teej vrats: "Harat-Aalika" recalls Parvati’s friend spiriting her away so she could win Shiva through penance rather than marry Vishnu at her father’s wish. Women keep a nirjala (waterless) fast and worship handmade clay images of Shiva-Parvati.
Cultural significance
Observed intensely in UP, Bihar, Jharkhand, Rajasthan and Maharashtra, and as Gowri Habba in Karnataka — falling the day before Ganesh Chaturthi, when Gauri is welcomed as Ganesha’s mother.
Good to know
The puja is traditionally performed in pratahkala (early morning); the fast runs sunrise to next sunrise without water for the most devout. Newly married women often keep their first Hartalika at their parental home.