There are situations where you use Zammad variables in triggers, text modules, signatures… but there is no way of adding or subtracting value to them. Eg. add 7 days (or 604800 seconds) to the Ticket last updated at variable.
The usage could look like this for adding 7 days to the updated_at variable:
{ticket.updated_at+604800}
In a Text module:
We have send you the package and will get in touch with you again in 7 days on the {ticket.updated_at+604800}.
Best regards