Can somebody confirm the minimum amount of time before the expiration of a passport is when trying to renew a non-immigrant b?

I am getting mixed messages about this. Is it 6 months or 1 year?

Thanks in advance

For a single entry non-b visa it is 6 months. For a multiple entry visa it is 18 months.

If you have an extension of stay (it is not a visa) from immigration there is no minimum but the extension will only be issued up to the date the passport expires. Then you have to apply for a new extension when the shortened one ends.

Thanks for the clarification. That helps a lot.