This is not true. Both the Jewish Encyclopedia and Spier's Comprehensive Hebrew Calendar discuss the five centuries future adjustment. Spier says it will be the task of a new Sanhedrin to make a decision as to when and how the calendar should be adjusted. Our Savior criticized the Scribes and Pharisees on many issues, but never on the calendar calculations. It has deceived some who are set to form their own independent church groups.
Calculation is necessary.