Hello @MarcosFe1,
This is not standard Adobe Campaign Classic behavior. When the campaign end date is consistently reset to start date + 5 days, it almost always indicates a custom configuration, not a product defect.
Based on experience, please check the following areas:
Custom typology rules (JavaScript logic)
Even if the typology rule is intended only for validation, any JavaScript-based typology rule can update campaign fields during execution or validation. A hard-coded duration (for example, startDate + 5 days) is a common pattern seen in custom rules.
Campaign template defaults
If the campaign is created from a template, verify whether the template enforces a default campaign duration. This can silently override manually entered end dates.
Calendars linked to the campaign or delivery
If a calendar is applied, Campaign may automatically adjust dates to fit allowed execution windows or validity periods.
Technical workflows or post-processing scripts
Some implementations use technical workflows or JS activities that update campaign attributes after creation or activation.
The fact that the end date is always set to exactly 5 days after the start date strongly suggests that a custom rule or script is recalculating the end date, rather than Adobe Campaign applying a system limitation.