From experience does anyone know what time of day United award seats are released to US Airways?

I'm trying to book an international award ticket and the return is right on the 330 day window. I've been calling in every day to extend the reservation to the newly available day while I have my hold on the seats. However, if I do it to quickly after midnight, the US Airways rep says that they can't see the seats yet, but the United site says they're available. By morning, the seats are accessible to US Airways.

I've reached my last opportunity to move the date during my 3 day hold but don't want to miss out due to waiting too late in the day.

Thanks!