Is the d in colonial days capitalized?

The word "colonial" is not capitalized when referring to the colonial period in general. It is capitalized when it is part of a proper noun, like "Colonial America" or "The Colonial Period."

Here's a breakdown:

Not capitalized:

* "Life in the colonial days was challenging."

* "The colonists had a strong sense of community."

Capitalized:

* "The history of Colonial America is fascinating."

* "The Colonial Period in North America was marked by significant changes."

So, the answer to your question is: no, the "d" in "colonial" is not capitalized unless it is part of a proper noun.