Network time

Question:

What is the difference between the following commands:

net time /setsntp:131.107.1.10

and

net time /set \\servername /y

I know the second command works for both Win9x and 2K/XP and synchs with an internal time source.

The first is only for 2K/XP to synch time with external sources. (Needed for domain controllers)

Are there two different clocks I am setting? Which one should I use for a global login script?

Thank you for the clarification