It seems that "Net Time" & "W32TM" are on different permission level (appears to require domain admin privilege) than timedate.cpl.
I couldn't change time with the first time commands, but with timedate.cpl, which calls the regular Windows Clock window, it works great.
So it remains a mystery as to why Net Time or W32TM gives me errors like:
"A required privilege is not held by the client." or
"The following error occurred: Access is denied. (0x80070005)"