Determine/Default Custom Date Fields in Form based on Another Custom Date Field

[Kmmaughs]

Hey! I have some date fields I'd like to auto-populate on the Create step based on the input of another date field. For example, I click Create to create a new issue, and I select a Date on one of the date fields. There are subsequent date fields that I'd like to then auto-assign a value to, but I still want the user to be able to override the defaults. 

Here's an example:

1. Click Create to create a new issue

2. Select a date for the custom date field called "Incident Date".

3. See the subsequent custom date field called "Plan Due Date" auto-populate with a date 7 days after the "Incident Date."

The user then has the option to override the value or continue as is before clicking Create to create the issue. 

I was playing with using a Behavior, but it's not really working. 

I tested the behavior on both the "Incident Date" field and the "Plan Due Date" field. Here's the server-side script I used:

import com.atlassian.jira.issue.ModifiedValue
import com.atlassian.jira.issue.util.DefaultIssueChangeHolder
import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.event.issue.field.CustomFieldUpdatedEvent
import java.text.SimpleDateFormat
import com.atlassian.jira.datetime.DateTimeFormatterFactory
import com.atlassian.jira.datetime.DateTimeStyle

def IncidentDateField = getFieldById("Incident Date") // Grab the Incident Date

def PlanDate = getFieldById("Plan Due Date") //Grab the Plan Due Date

double dDays = 7 // Defined number of days

if (IncidentDateField.value != null) {
PlanDate.setFormValue(new Date().plus(dDays.toInteger()).format("dd/MMM/yy hh:mm a"))
}