You can alter the process escalation time with an action rule. Go to the Steps heading in the Designer navigation menu. Click Rules next to the desired step, then New in the action bar to display an overview of rule types. Select the action rule. The form box for this rule type appears. In the section Process escalation rules, enter a new number and/or select a new time unit for the processing deadline for the process. Lastly, click Save to save your changes.

Process escalation
Please note: If you want to define a specific date as the completion time, the entry has to be in the YYYY-MM-DD format (e.g. 2018-05-11).
There is more detailed information on action rules in chapter Action rule.