Problem:
Sometimes Dreamweaver will give a message:
"Dreamweaver cannot determine the remote server time. The Select Newer and Synchronize commands will not be available."
Reason:
This is because Dreamweaver cannot write a file to your hosting account which it needs to create in order to determine the time on your server. This is typically because your account is over it's allotted disk quota, or, there are permissions problems on your site. More often than not, it is because your account has exceeded it's quota.
Solution:
Delete unneeded files or upgrade to the next hosting package so that you have more space available.
If you have enough disk space, you may want to check that you have enabled "Use Passive FTP" in your Dreamweaver remote site definitions. Sometimes Dreamweaver file transfers / commands will fail if passive mode is not enabled.
Source:
Adobe.com : Troubleshooting FTP issues
To get the server's time stamp, Dreamweaver creates and deletes a folder named XYIZNWSK. There may be server permissions problems that don't allow Dreamweaver to create or delete folders. For more information on this issue, see Synchronize and Select Newer options are not working correctly (TechNote tn_14413).