Does 2 mg.of Valium help you with anxiety all day?

First off I agree with Wildcat, everyone reacts differently to medications.

Have a look at the following information:

https://www.drugs.com/dosage/valium.html

Source: Drugs.com

Hi, Shabangy!
Every person will respond differently to medications so it will depend entirely on how it affects you personally.
2mg is a relatively low dose but you could potentially feel the effects for as long as 12 hours more or less.