A computer-implemented user authentication method to provide users of computer devices interconnecting with computer information systems with a frequently changing numeric passcode generated via a time-synchronized mathematical operation of the mathematical constant Pi (π) without the need for a Two Factor Authentication process. The method operates the mathematical constant Pi, wherein an application software performs the mathematical operation of Pi to select a segment of Pi. The selected Pi segment becomes the user's passcode, referred in this invention as the PI ID Value (PIV). The method is dynamic, creating a new PIV for the computer user each time the user operates his/her computer device to gain access into a network or website. To attain the same Pi segment in real-time and authenticate the user, the network or website administrator utilizes in its computer server the same parameters and mathematical operation used by the user's computing device.