Date cell is not calculating correctly
I have a sheet where I want to add 30-days to another cell that is a date.
I am using the formula: =(original date cell) + 30
Example: The original cell has a date of 3/19/19. I should get 4/18/19.
However, I'm getting 3/19/1930.
I have cleared the cell contents, deleted the row, and whatever else I can to create a clean cell format. What's up??