Difference in Dates

I am trying to determine the number of days since the last check in from a computer.  Currently my code is:

=DATEDIFF(DateInterval.Day, GetDate(),CDate(Fields!Last_SCCM_Hardware_Scan.Value)) 

but I am getting the error:

[BC30451] Name 'GetDate' is not declared.

Can anyone help?

Thanks,

-Nick