cant get cells to stay blank when no date is entered in other cells

[steve400243]

hello, I have a problem that i'm sure will be an easy fix but i am stumped and cannot get it to work right. The DELIVERED date is in column "O", the "LFD" column is "p". I want the LFD date to populate automatically once the delivered date is manually entered. the LFD date is the delivered date + 4 days. The problem I am having is that If there is no date in the delivered column i want the cell in column P to be blank. When i copy down the column i get the date reference of 1/4/1900? Thanks for all help.

DELIVERED	LFD
9/21/2017	9/25/2017
9/22/2017	9/26/2017
	1/4/1900

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</tbody>

 

[Tetra201]

... If there is no date in the delivered column i want the cell in column P to be blank...

Try

=IF(ISNUMBER(O2),O2+4,"")

 

[steve400243]

Try

=IF(ISNUMBER(O2),O2+4,"")

Excellent, thanks very much for your time. I appreciate it!