When trying to access preview docs, I am directed to:

https://dynamicsinsiderdev.blob.core.windows.net/downloads/a312cab61f13e8118140e0071b6aa0e1/Private%20preview%20documentation.pdf?sv=2015-07-08&sr=b&sig=HVXjGC1noUCQrfH5F%2F7ynt%2BXL0rbFTsTAyA%2B3QDjCmE%3D&se=2018-02-16T14%3A42%3A14Z&sp=r

And it returns:

<?xml version="1.0" encoding="UTF-8"?>

<Error><Code>AuthenticationFailed</Code><Message>Server failed to authenticate the request. Make sure the value of Authorization header is formed correctly including the signature. RequestId:730e34a5-001e-00cb-158b-aa8cc0000000 Time:2018-02-20T20:41:59.6031749Z</Message><AuthenticationErrorDetail>Signed expiry time [Fri, 16 Feb 2018 14:42:14 GMT] must be after signed start time [Tue, 20 Feb 2018 20:41:59 GMT]</AuthenticationErrorDetail></Error>