To change a reservation date before the renter has paid (status either "pending", "discussion", "pre-paid" or "pre-approved"), go to the conversation page of the concerned reservation and click on "Make an offer".
To change a reservation date after the renter has paid, (status either "paid" or "validated / deposit paid"), go to the conversation page of the concerned reservation and click on "Modify reservation". The renter will then have to validate the change of dates after being notified by email.
If the change of date is not validated by the renter, the rental will remain at the initial date.