# How is an AC signal offset?

In three-phase the 2nd and 3rd phase are offset by about 120 degrees($\frac{2\pi}{3}$ radians). But how is this achieved?

The concept that just each phase is offset by 120 degrees sounds easy but designing a circuit for this looks more difficult.

Does it go back to when the electricity is generated at the power station or done later on in the transmission?

For example each generator is configured to generate one phase slightly later than another?