Option 1 -> This is when the merger officially took effect on January 26, 2020, through the Dadra and Nagar Haveli and Daman and Diu (Merger of Union Territories) Act, 2019.
Option 2 -> This is one year after the actual merger date, making it incorrect.
Option 3 -> This is two years after the actual merger took place, making it incorrect.
Option 4 -> This is three years after the actual merger occurred, making it incorrect.
Hence, Option 1: January 2020 -> The merger was implemented on January 26, 2020 (Republic Day), combining the two Union Territories of Dadra and Nagar Haveli and Daman and Diu into a single Union Territory under the legislation passed in 2019 -> correct