MVAs are associated with TRACONs and MIAs are associated with centers.

Both are based primarily on obstacles and containment within controlled
airspace. They don't change at all, except when a periodic review is
conducted.

But, a few TRACONs, such as Palm Springs, CA, close at night so the much
higher center MIAs take effect. The MIAs are higher because they have
larger buffers (less accurate center radar) and usually cover larger areas.

Having said that MVAs and MIAs don't change. Altitudes available for
assignment often change because of airspace agreements between TRACONs
or between TRACONs and centers. But, those restrictions are quite
different than MVAs.

Robert M. Gary wrote:
Not sure about AZ but in California the min altitudes often change with
time of day as well depending on what facility is open.

-Robert