$$366$$ days $$=52$$ weeks $$2$$ days.  Jan $$1$$ $$1988$$ is $$52$$ weeks $$2$$ days before Jan $$1$$ $$1989$$. This date in $$1988$$ is $$2$$ days before Sunday so it is on a Friday. 
January $$1$$, $$1989$$ was a Sunday. January $$1$$, $$1988$$ (a leap year) was a． 
  Friday 
  Saturday 
  Sunday 
  Monday 