Thank you for your post.
I am unable to replicate the issue. This is what I have done:
1. I created a new table "timestamp" with a Timestamp field named "TS", and set it for global storage.
2. I created a script, "GetTimeStamp", with the following steps:
Set Variable [ $notglobaltimestamp ; Value: TS ]
Set Variable [ $$globaltimestamp ; Value: TS ]
Show Custom Dialog [ $notglobaltimestamp ; $$globaltimestamp ]
3. In Browse Mode, I added a record, and entered into TS: 5/7/2015 12:45:00
4. With the Script Debugger and Data Viewer active, I ran the script "GetTimeStamp", and the seconds showed for both the local and global variables (See screen shot below).
Let me know what I'm doing differently than you so I can replicate the issue.