"We haven't had to go to Sundays before, at least not as far back as people can remember," said spokesman Jonathan Gust. "This has just been an exceptional situation."
Saturdays are not an option, he said, because classes and activities already are held that day.
Villanova's faculty will also have the option of making up classes through online teaching.
School districts extend the school year to meet the required number of days of instruction they must provide, but colleges have the flexibility to make up the class time in other ways. Also, it is very difficult for colleges to extend the academic year.
"They are able to shift to the use of more technology to stay connected with their students when meeting face-to-face is not possible," said Anne Skelder, provost and vice president of academic affairs at Cabrini College in Radnor, which has lost eight days.
The University of the Sciences has lost six days, and the faculty is working on how to make up the time, spokesman Brian Kirschner said.
"They have various options, such as online presentations [or] discussions, Saturday classes, and evening hours," he said. "By using these and other strategies, they have already cut the hours missed by two-thirds."
Some universities are unsure how they will make up for the missed time.
West Chester University has closed seven days, including Thursday and Friday, the most that officials can remember so close to the start of a semester. Preliminary discussions are underway on how to make up the time, school spokeswoman Pamela Sheridan said. The university wants "to get through the next couple of weeks to ensure winter storms are behind us before implementing anything," she said.
Immaculata University has missed seven days, not counting delayed openings. "Each professor is in charge of making up assignments for his [or] her class," said spokeswoman Lydia Szyjka.
On the low end, Temple and La Salle Universities have lost three days.
"We have not added any days to the semester, nor are we taking days away from any breaks," said spokeswoman Eryn Jelesiewicz, who said professors were using online instruction.
La Salle spokesman Jon Caroulis said "faculty have been asked to assign extra work."
One college that will not have to worry about making up any time is Swarthmore. It stayed open through the subzero temperatures, freezing rain, and this week's nor'easter. Last week, a power outage did not stop it. Professors had the option of holding classes, and many did, spokeswoman Alisa Giardinelli said.
"There was an actual dissection that continued," she said, with the help of an emergency light and window light.