- August 20, 2026
- By Sala Levin ’10
If the University of Maryland relied on medieval-era timekeeping tech, a lot of students might show up for the fall semester in June or October.
For most people, though, the giant sundial at the middle of McKeldin Mall is only decorative, and few have noticed that for the past 35 years, while the time is right, the scale that shows the date has been off by up to several months.
The few who did notice, however, happened to be in the departments that concern themselves with orbits of the celestial bodies that sundials depend on. Following a gentle request from astronomy Chair Andrew I. Harris, the university this week reset the clock, so to speak.
“Now, our sundial will actually be a compliant sundial,” said Harris.
As part of a routine refinishing of the sundial, workers are now fixing the date markers along its northern extension, meticulously measuring the location of the month, solstice and equinox markers and reinstalling them.
A plumb bob, the hanging instrument, measures the true vertical line of the sundial’s gnomon (the blade that casts a shadow).
The sundial debuted on McKeldin Mall in 1966, a gift from the Class of 1965 with the assistance of the then-combined Department of Physics and Astronomy. In 1991, as part of the installation of the ODK Fountain and the plaza that bisects the mall, the sundial was removed and reinstalled in its current spot, where it was placed within a brick circle.
The full history is murky, but it seems likely that during that move, landscape architects set the sundial so that the extension that marks the date aligned with the edge of the circle. There was just one problem, said Harris. The brick circle wasn’t designed with the sundial in mind; lining up the northern extension with the edge of the circle meant that the month markers weren’t positioned to track the date correctly.
Students using the sundial as a jungle gym haven’t helped matters, said Karen Petroff, director of landscape and special services in Facilities Management (FM). By dangling from the edge of the gnomon (the term for the vertical blade on the sundial that casts a shadow), they bent it from its original orientation.
Determining how to set the month markers is straightforward, according to Harris. First, measure the gnomon. Then, calculate the height and angle of the sun on any given day at noon. Combine these pieces of information, and you can work out where the gnomon’s shadow will land—and thus, where the markers should go. (Okay, it’s straightforward if you’re a professor of astronomy.)
The brass plaques that denote the months, solstices and equinoxes are being placed in their correct spots to one-sixteenth of an inch.
Rumblings of the sundial’s inexactitude have circulated for years. On Nov. 3, 2022, Harris walked over to the sundial to observe a celestial event happening that day: the largest annual disparity between what the sun and clock consider to be noon. While there, he noticed that the shadow from the gnomon fell far beyond the November marker, going past even the February marker. He reported his findings back to the astronomy department in his weekly newsletter, and later, he and student Ian Stringer ’19, ’25 went back to work out the sundial’s geometry.
Harris saw an opportunity to raise the issue with FM when he received a notice earlier this summer that one of its teams would be refinishing the sundial’s concrete pedestal. He reached out to Petroff to ask whether this would be a convenient moment to fix the seasonal markers.
She was enthusiastic, and this week, Harris joined Petroff and several FM workers to review his measurements and lay out exactly where the month markers should be reinstalled. The masons are taking care to set the markers’ new locations to within one-sixteenth of an inch.
The astronomy department is pleased that there will be a happy resolution to what’s become a friendly inside joke. No longer will the planet-watchers be able to apply the moniker one grad student gave the malfunction: “#scandial.”