If you sort transactions based on date, they will not be in chronological order. The millenium bug may cause additional problems. The UC student record system contains a millenium bug. To check for bugs it is necessary to run test data through the program to ensure it operates properly. Beta release software normally has an expiry date - it will not run after that date.
Some bugs are deliberate.
One programmer programmed a bank's computer to transfer all rounded amounts to his account. Programmers pose a major control risk. Separation of duties must be rigidly imposed on programmers. They are not to have access to any assets or to the operations of the computer system. Before a programmer updates a program, the update must be tested and approved by a supervisor.