Hindus do make it a point to celebrate Krishna Janmastami in the "month of Shravana Ashtami tithi Krishna paksha". The birth of Rama is celebrated on "Navami Tithi during Shukla Paksha of Chaitra month" as Rama Navami. These and many other revered Saints' Birthdays are celebrated as per their Tithi.
The calculation of Tithi birthday as per Hindu Lunar calender has been an ancient indic tradition. But, when it comes to our own birthdays we are not much aware of our Hindu Lunar Tithi birthdays. This website is an effort to encourage more Indians to celebrate birthdays based on our tradition. Mapping festivals to the tithi dates also helps us track our birthdays by referring to any Calenders in our homes. Festival references have been given from websites like DrikPanchang which is a wonderful source of information. Vivah Panchami celebrated on Panchami, Margashirsha, Shukla Paksha is the wedding anniversary of Shri Rama and Devi Sita. Similar Tithi Calculation can be done for Wedding Anniversary as well.
Ancient indians devised a highly accurate calendar based on the movement of the Sun,moon and stars. This calendar measures a unit as tithis which is a 12 degree (=360 degrees/30 tithis) change in the size of the phase of the moon. A nakshatra is collection of stars that represent position of the moon in the sky (=360 degrees/27 Nakshatras) in a indic month. The month starts from new moon (amavasya-anth). While some traditions start month on full moon (purnima-anth), the birthday dates and time calculated and show here remains consistenly correct across both. This indic calendar is unbroken since millenia (read here how the gregorian calendar is broken in 15/17th century)