Question

how to make a sentence with observance

Answer 1

This is an example of how to use observance in a sentence, however I personally find it difficult to use observance in a sentence.

"In observance of Memorial Day, we attended a parade."

I hope this has helped you.

Answer 2

Example:
The frequent Old Testament association of "new moons and Sabbaths" may point to an original observance of the 1st and 15th days of the month.