Calculated Date column based on a Date from another list

[Najwa_Work]

Hello All,

I am new to this forum. I started with Sharepoint a month ago and I have a question as I was guided to this site and would really appreciate your help on the below matter. I was wondering if Sharepoint List can perform basic automatic formulas as excel.  Below is the description : 

I have created :

A- List A ( only one item)  with a Date column "Start"  

B- List B ( several items) with a Date column "Deadlines" 

The following is targeted : 

1. That Deadline in List B will be automatically populated once "Start" in List A is filled/edited as per below.  The user will only input only one data which is "Start". 

• Item_1_Deadline = "Start" +7 days 
• Item_2_Deadline= "Start" + 14 days 
• Item_3_Deadline ="Start"+ 21 days 

I tried with lookup column, however lookup column does not automatically fill/populate a column in Sharepoint, additionally it is not possible to execute a formula with a Lookup column values. 

if it is possible with json code formatting , I would appreciate guidance on where I can get the info. 

Your help is highly appreciated. And If you require additional information  I am more than available to provide it . 

Thank you. 

Najwa. 

[#2 · Accepted solution]

@Najwa_Work you can use PowerAutomate or a SharePoint Designer Workflow (that's the old way). Trigger when a new item is created in List A and then use the Flow to create 3 items in the second list.

One thing to consider is the number of items that may get generated in List B. If all of the dates relate to the same item, then you may be better just having the 3 dates in List. 

[#3]

HI @SteveKnutson , Thank you for your help I will use the new Flow of PowerAutomate. 

Thx. 

Najwa.