I need to do date calculations in Zoho Creator.  Can someone help with this?

Here are the various calculations I need to do.  I'm a volunteer book review editor, and need to keep track of books I've assigned to reviewers.

I need to log in the date a book is received by a reviewer, add 30 days to it, and generate a date the review is received.  I also need to take today's date and subtract the date the book was received, and get a number of days the book has been out.  Finally, in a perhaps simpler calculation, I need to look at the date the review was received, which I enter manually, and generate the word "Done" in a field I call "Status".

The field names are "Date Book Received," "Date Review Due," "Days Out", and "Status".  The first two are defined as date fields; the third as a numeric field, the fourth as a single-line text field.

Thanks so much for any help you can give.