What determines visa time stamped on I-94 by Port of Entry?

[shahn]

Suppose parents get visa from Jan 1 to June 30.
Land in US on June 1.

How long will the visa be on I-94 stamped by Port of Entry officer?

Thanks a lot.

[usadesi]

Usually I-94 would be same as visa expiry date, some times may get a week more.