The Academic Staff College organized a refresher course in six different subjects, only one on each day, from Monday to Sunday.

I. One of the days was a holiday.

II. Psychology was on the previous day of the holiday.

III. The course ended with History.

IV. Economics, which was taken up on Wednesday, was on the previous day of Physics.

V. Psychology and Philosophy had a gap of two days.

VI. There was gap of one day between Sociology and Economics and a gap of two days between Sociology and Physics.

Which day was a holiday?