Mar 8, 2017 - 5:20 PM
in reply to yjingyi
Hi yjingyi and welcome to MySwissAlps!
Yes, the start date is mandatory and cannot be changed once purchased. You could cancel the pass but that would incur a penalty of 15% I believe.
I wouldn't buy the pass until you are 100% sure on your dates. There is no rush to get the pass - they can't run out of passes to sell. Just ensure you buy the pass with enough time to have it mailed to you or emailed and printed at home before you travel.