Hello all, newbie to forum, hoping you can help my enquiry. I have 2 tickets booked LHR ZURICH SIN for 6 day stay in October 2020. I understand SWISS will allow a change to this ticket and I was hoping to move the dates to beginning of 2021. My 2 questions:
1. When should I call SWISS to change ticket dates?
2. Will SWISS allow a longer stay e.g. 2 weeks when the original ticketing was only for 6 days?

Thank you.