The Embassy of Belgium in New Delhi is open from Monday to Friday, from 9 am to 5 pm, except on public holidays. The list of public holidays can be found on the following link:
http://india.diplomatie.belgium.be/en/embassy-and-consulates/embassy/public-holidays
The Consulate General of Belgium in Mumbai is also present on Facebook: https://www.facebook.com/Consulate-General-of-Belgium-in-Mumbai-1082220548469696
The Consulate General of Belgium in Chennai also has a Facebook page: https://www.facebook.com/Consulate-General-of-Belgium-in-Chennai-144735729202653/