From 138 years of French rule to an Indian Union Territory
Background
All the regions of Puducherry were under French rule for 138 years. On 1 November 1954 the French possessions in India were de facto transferred to the Indian Union and became a Union Territory. Only in 1963 did Puducherry become officially an integral part of India. Puducherry still has a large number of Tamil residents holding French passports, whose ancestors were in French government service and who chose to remain French at the time of Independence. Apart from monuments of the French period, the territory has a French Consulate and institutions such as the French Institute, the Alliance Francais and the Ecole Francais d'Extreme Orient, along with the Foyer du Soldat for war veterans of the French Army.
In plain words
De facto transfer Transfer in practice before legal completion — Administration passed to India in 1954 while the formal legal transfer was completed later.