Valium BID. 12 hours.
Ask your doctor. Prescriptions come with instructions about how to take them. If it simply says twice daily, this usually means around 9 am and 9 pm. But medicines for anxiety are often given "as needed", meaning twice-daily is a maximum, not a requirement. Check with your doctor about what he or she meant — it's best not to guess. There are also non-medication ways to help anxiety, and other medicines too.
Don't take it at all. Valium is a benzodiazepine with high risk for addiction. If used it should be for short term , at least 8 hrs apart but it's better to look ands ask for better alternatives for anxiety , insomnia or muscle relaxation.They are many other medications that can be used for those purposes that don't have the risk of addiction and tolerance.