why do we celebrate republic day on 26th january though the constitution was adopted in 26th november?

Ummm...answer to this question lies in history. In 26th jan 1930, lahore session of congress, Jawahar Lal Nehru declared that, Congress will demand for Poorna swaraj frm british and passed resolution for this. So though consitution was adopted on 26 Nov, it was offically adopted on 26th Jan, in memory of above mentioned day.