The Calendar of the college year was described in the early laws in 1783 in terms of the three vacations which were scheduled from September 6 to October 20, from December 24 to January 10, and from April 21 to June 1. The Laws of 1803 changed the dates of vacation to allow four weeks after Commencement, which occurred the first Wednesday in September, six weeks beginning the last Wednesday in December, and three weeks beginning the first Wednesday in May. In 1807, in order to provide students with more time in the winter when they might earn money teaching in the district schools, the winter vacation was lengthened to eight weeks and the spring vacation was shortened to two weeks and began the third Wednesday of May. Seniors were examined in languages before the spring vacation, and in other subjects in mid-July, leaving them free after that time to prepare their parts for Commencement. The other classes were examined each year before spring vacation and again before Commencement. President Wayland shortened the winter vacation to six weeks in 1827. 1832-33 was the last year that there was a vacation after Commencement. The next year the first term began immediately after Commencement, the winter vacation was reduced to three weeks, and the third term ended in July.
The Laws of 1850, which introduced the “new system,” called for two terms instead of three. The first of twenty weeks began on the first Friday of September. The second term of the same length began after an eight week vacation on the fourth Friday of February. Commencement was then held in July. In 1853 the date of Commencement was changed back to September by popular demand, but the two term calendar remained the same. After Commencement was moved to the last Wednesday in June in 1870, the calendar was changed in 1871 so that the first semester ended in mid-January and the second began on February 9 after a three week recess, ending just before Commencement. There was a week off at Thanksgiving and another in late April. In 1875 Commencement was changed to the third Wednesday in June, and another change in the calendar took place. The first term began on the third Wednesday in September, and the second term began immediately after the mid-term examinations, as the winter vacation had been abandoned. Three days were allowed at Thanksgiving, ten at Christmas, and the spring vacation was extended to nine days. In 1891-92 the two semester year was replaced by three terms, beginning in early September, late December, and late March. In September 1911 there was a return to the two-term system, in which the first semester ended in February. In 1919 there was a summer session to enable students whose work was interrupted by the war to make up time.
Year-round operation began in 1942 with a summer semester added as the University pursued an accelerated program adapted to the education of members of the armed services during the Second World War. The three-semester year ended in June 1947. In 1948 two summer sessions with an enrollment of 964 in the first and 837 in the second were held to alleviate problems of crowded laboratories during the year and the desire of the veterans to make up for lost time in completing their education.
In November of 1981 the Faculty voted to change the calendar beginning with the 1983-84 academic year. Previous proposals had been defeated in 1974 and 1977, but polls had shown the a majority of the students wanted to have first-semester examinations scheduled before Christmas. Accordingly, the new calendar called for the first semester to begin on the day after Labor Day, and end by December 20, broken only by a three-day Columbus Day weekend and a four-and-a-half day Thanksgiving weekend, and the second semester to begin the third or fourth week in January and end between May 15 and 21. Commencement was rescheduled to the last Monday in May. In 1984 the Office of Summer Studies was established under Professor Reginald Archambault. Among the summer programs were some undergraduate courses, along with summer courses for teachers and pre-college students.