Ask an Anglo-Indian family what matters and they will mention church, family, maybe the food. Watch the year and it is obvious: Christmas is the fixed point everything else arranges itself around.
Someone marrying into the community who understands only this will do better than someone who has learned everything else.
What it actually involves
It starts in November. The baking — kul kuls, rose cookies, dodol, marzipan, the cake fed with rum for weeks. This is not preparation for the day; it is a substantial part of the thing itself, and it is done together.
The house fills. Relatives who live elsewhere come back. Families who have not seen each other since last Christmas see each other.
It runs for days. Midnight mass, the day itself, visiting, more visiting, and on to New Year.
People come home. Perth, Toronto, London. For many families the only time the whole family is in one country.
Why it carries so much
For a community that lost its institutions, Christmas is the one thing that reliably gathers everybody. The colonies went, the clubs aged, the network thinned — and this stayed.
It is not only a religious festival. It is the annual proof that the family and the community still exist in one place.
If you are marrying in
Do not arrange anything else in that fortnight. Not travel, not a work commitment, not a visit to the other side of the family. It will be understood as a statement whether or not you meant one.
Learn to make one thing. Badly is fine. Turning up and helping with the kul kuls will earn you more goodwill than a year of being agreeable.
Expect the house to be full and expect to be introduced to a great many people whose exact relation to each other nobody will be able to explain.
If you are the family
Say this out loud rather than assuming it is obvious. It is entirely possible for someone to spend two years in a family and not realise that missing Christmas is not the same as missing a festival.
Whatever else has faded, this is the thing the community still does together. Understanding it is most of understanding the family.