Earliest date and time from linked work items

Return the earliest date from a Date Time Picker custom field in the linked work items of the current work item.

Configuration

Create a Custom smart text field and use the Jira expression parsing mode.

Expression

CODE

let minDate = issue?.links.map(link => link.linkedIssue.customfield_nnnnn).filter(
d => d != null);
minDate.length > 0 ? new Date(minDate.reduce((a, b) => a < b ? a : b )).toString() 
: ""

Please, replace nnnnn with the ID of a Date Time Picker custom field.