How to create an automation rule to add days to a date field?

[Shahriar]

Hi, 

I have the following date fields:

• Target start
• Target Discovery End Date

I am trying to create a very simple value change automation. 

When I change or set a date in the "Target start" field, I would like the "Target Discovery End Date" field to display a date that is 3 days later than the date in the "Target start" field. 

I am using the following Smart values expression, but it is not working:

{{issue.Target start.plusBusinessDays(3)}}

What am I doing wrong? What is the correct way to write this expression? 

Scenario or example:
If I add or change the "Target date" to 11/10/25
I want the "Target Discovery End Date" to display 11/13/25

They are both date fields.

Thanks, 
Shahriar

[Gor Greyan]

Hi @Shahriar

Thanks for the question.

Try to find the customfield ID for the Target start field and use this expression.

{{issue.customfield_12345.plusDays(3)}}

Also,

.plusDays() → adds calendar days
.plusBusinessDays() → adds business days

Let me know, if this worked or not.