How to change iPhone clock US ti

Settings > General > Date and Time > Set Automatically (on) this will change the time on your phone to where you are located. If you then turn this off, the time will set and it will save battery life.

If you want to change it to a different area of the US / city you are not located in, you can do this too while in this area of settings.

If this doesn't work take a look at this

If you can’t change the time or time zone on your iPhone, iPad or iPod touch – Apple Support