The Republic Day is one of the most eagerly-awaited days for India and especially for the children because they love to watch the Parade carried out by various wings of the military and armed forces and also many displays shown by other departments and States of the country. Even if you are not able to physically attend the Parade in Delhi, you can still admire the beauty and majesty watching it on the TV.
If you want to know how to say Happy Republic Day in Hindi, the below phrases will help you. The Republic Day is called गणतन्त्र दिवस in Hindi.
So, Happy Republic Day would mean:
गणतन्त्र दिवस की बधाई