Hi.  I wonder if someone can help me.  I'm a volunteer book review editor.  I use Zoho Sheet to keep track of books out.  I have a column where I keep the date a reviewer receives a book, and another column that tracks when the review is received.  I check that the date reviewer receives the book not empty, and that the date the review is received is empty.  The reviewer has the book, but has not submitted a review.  In another column, I'm wanting to compute the date the review is due -- 30 days from when the book is received by the reviewer.  I've tried the following formula in the Date Review Due field --  =IF(AND( K2 <> "" ; N2 = "" );NOW()- K2 ; "" )

The result is a date in 1900.l

I've attempted to attach a screen shot.  If anyone can help, I'll be very grateful.