because the reference frame for tcb is not influenced by the gravitational potential caused by the solar system, tcb ticks faster than clocks on the surface of the earth by 1.550505 × 10 (about 490 milliseconds per year). consequently, the values of physical constants to be used with calculations using tcb differ from the traditional values of physical constants (the traditional values were in a sense wrong, incorporating corrections for the difference in time scales). adapting the large body of existing software to change from tdb to tcb is an ongoing task, and many calculations continue to use tdb in some form.