Query system time from linked server

I set up a linked server in my local sql server and my sql like this:

select DATEDIFF(day, T.running_Date, GETDATE()) AS [Cycle time],
FROM   Linkedserver.testdb.dbo.testtable T

running_date is the linked server time, but getdate() function just return my local sql server system time. How can I get linked sql server system time, pls. help!

thanks a lot!

Sidney