Featured Post from University of Delaware

The science of leap day

Feb 29, 2024

3 min

John Gizis


The arrival of a leap year brings with it myths, legends and superstitions about its origin. John Gizis, professor of physics and astronomy at the University of Delaware, takes part in a Q&A to share the truth and science behind this “extra” day added to the Gregorian calendar every four years.


Why do we have leap day?

Unfortunately, the amount of time the earth takes to go around the sun is not exactly 365 days. It’s off by about ¼ of a day each year.


It would be hard to have a calendar for 365 ¼ days. When was the extra day added to the calendar?

Julius Caesar introduced the Julian calendar in 46 B.C., which added one extra day every four years. Of course, the year is not exactly 365 ¼ days either, so after a while, that extra time built up. Pope Gregory XIII established the Gregorian calendar [the current calendar] in 1582 to correct the fact that the calendar had gotten off by about 12 days, enough that it was noticeable.


How was it noticeable?

The seasons were gradually shifting, so that what we think of as summertime in the northern hemisphere had gradually become more like autumn. The shortest day of the year is Dec. 21. Basically, the shortest day of the year drifted and eventually was in early December.


How did they institute the reforms?

First, they skipped a couple of weeks, so they returned to the original calendar lining up with the sun and stars as it’s supposed to. Then they instituted a couple of rules to keep this from happening again. Leap year happens in years divisible by four, but every 100 years, there is not a leap year. However, every 400 years, you do have a leap year. This happened in the year 2000. And the next time it will happen most of us won’t be around — 2100 will not be a leap year.


What would happen if the extra day had not been introduced?

If we didn’t have it at all, we would be off by ¼ of a day every year. The seasons would completely shift through the calendar and anything that ties to the seasons would be affected, like farming. It would create havoc with the time to plant and to harvest crops, for example. You also would lose the meaning behind sayings such as “April showers bring May flowers.”


Multiply the 2,000 years since it was introduced by ¼ day per year, and that would be 500 days we would have shifted over history. In the northern hemisphere January would have become summer, then gone back to being winter, then shifted off again.


Does adding the extra day make up the difference exactly and keep the astral year in sync with the calendar year?

Yes, but this relates to a bigger issue. Astronomers want time to match up so that the positions of the stars match up year after year. Because the length of day changes slightly over time, astronomers sometimes would like to add an extra “leap second” to keep the stars in sync with our time system. But adding a second is an annoyance for computer and tech systems.


Did you know that people born on leap day are sometimes called “leaplings?” According to Google, in 2020, there were about 5 million people with Feb. 29 birthdays. Do you think they have any advantages or disadvantages to being born on this day?

No, I didn’t know that, and I know someone who refused to be induced on that day because she didn’t want confusion for her child, although I think it might be cool. After all, in this day and age, everyone always knows how old they are.


To set up an interview with Gizis, visit his profile and click on the contact button.

Connect with:
John Gizis

John Gizis

Professor, Physics and Astronomy

Prof. Gizis focuses his research on improving the understanding of stars and brown dwarfs (failed stars).

Brown Dwarfs and BinariesCool StarsStarsSolar SystemCosmology

You might also like...

Check out some other posts from University of Delaware

2 min

UD physicists track one of the most powerful solar flares in nearly two decades

A massive solar flare – possibly the strongest recorded in nearly 20 years – has unleashed a wave of charged particles toward Earth, sparking radio blackouts across parts of Africa and Europe and triggering measurable increases in radiation levels worldwide. At the University of Delaware, physicists Pierre-Simon Mangeard and John Clem are closely monitoring the event through UD’s neutron monitor network, a global system that tracks cosmic radiation from observatories in Newark, Greenland, Canada, Antarctica and Hawaii. “This is a significant event, still in progress,” said Mangeard. The physicists are seeing a roughly 65% increase in ground-level radiation, which is possibly the largest since 2006.  These elevated readings are known as a Ground Level Enhancement (GLE) – a rare occurrence caused by high-energy particles accelerated by solar flares that penetrate Earth’s magnetic field and reach the surface. The data being collected now will help researchers better understand how such bursts of solar activity impact Earth’s atmosphere, communications systems and even aviation safety. Clem and Mangeard’s work at UD’s Bartol Research Institute and Department of Physics and Astronomy contributes to global efforts to monitor and predict space weather events, including solar storms and coronal mass ejections. The team’s continuous, real-time data help scientists worldwide assess potential disruptions to satellites, power grids and high-altitude flights. As analysis of this flare continues, UD’s neutron monitor network will remain a key resource for understanding how space weather events ripple through our planet’s systems. Experts available for interviews: Pierre-Simon Mangeard, research rssociate, Department of Physics and Astronomy John Clem, associate professor, Department of Physics and Astronomy To contact Mangeard or Clem, email mediarelations@udel.edu.

2 min

Acing AI interviews: Career expert on strategies for job seekers

AI-recorded interviews are becoming a standard step in the hiring process, but many job seekers still aren’t sure how to handle them. University of Delaware career expert Jill Gugino Panté says candidates should treat these algorithm-driven interviews with the same seriousness as traditional ones and details how this can be done. Panté, director of UD’s Lerner College Career Services Center, can discuss what today’s AI interview platforms really measure – from confidence and tone to eye contact and facial expressions –  and how job seekers can stand out. She can also explain what recruiters are looking for in the AI-generated summaries that often determine who moves to the next round. Panté’s expert tips include: • Check equipment to make sure everything is working and the software is updated; turn off all notifications to avoid distractions and set up the space with good lighting, a neutral background. • Smile and maintain your energy, as some AI software will assess your tone and engagement. • Prepare as you would for any other interview - review the job description, research the organization, use the STAR method (Situation, Task, Action, Result) when providing examples. • Be sure to look at the camera and not the screen. It might feel awkward but that’s technically where the "eye contact" will be. • Some platforms will allow you to review your recording before submitting. Use this opportunity to take notes about your body language, pacing and clarity. To contact Panté directly and arrange an interview, visit her profile and click on the connect button. Interested journalists can also send an email to MediaRelations@udel.edu.

3 min

From classrooms to communities: Rethinking civic engagement in K–12 education

When national headlines focus on school board battles and political polarization, James Bridgeforth, assistant professor of educational leadership at the University of Delaware, is focused on what’s possible instead: building a more inclusive, participatory model of democracy through public education. His research in UD's College of Education and Human Development explores how community voice, equity and local leadership intersect to shape education policy – and how school boards can serve as vital engines for rebuilding public trust in government. "Despite the often sensationalized stories of chaotic school board meetings and the influence of more national "culture war" issues, I still believe that it's possible for people from different backgrounds, experiences, and points of view to come together to figure out how to best serve the needs of all of our children." – Bridgeforth Bridgeforth’s work centers on education governance, policy and leadership, with particular attention to how racism and anti-Blackness manifest in schools and policymaking spaces. His scholarship highlights the importance of inclusive decision-making, arguing that effective education policy must be representative of the diverse communities it serves. He recently published the report "Navigating Democracy in Divided Times" with co-authors on this topic. As part of his work with the Getting Down to Facts III project at Stanford University, Bridgeforth collaborates with researchers studying how to improve California’s TK–12 system and inform the next governor’s education policy agenda. His work documents the complex realities faced by local school board members – often minimally paid community leaders navigating contentious public discourse, social media pressure and limited resources. He notes that this research can be applied to school boards around the country.  The next frontier: Youth civic engagement Over the next several years, Bridgeforth aims to deepen understanding of how schools can nurture young people’s civic skills and leadership capacity through participation in governance. One proposed project – "Strengthening Opportunities for Youth Civic Engagement and Student Voice in Educational Governance" – uses participatory action research to explore how student board member policies and engagement practices foster civic agency and democratic mindsets. This collaborative work brings together youth-led community organizations and education researchers to study how these experiences shape long-term civic behavior – from voting to public service. Why it matters Bridgeforth’s research arrives at a pivotal time for American democracy. As trust in public institutions erodes, local school boards remain one of the spaces where citizens can directly shape policy. His work points to a hopeful truth: democracy’s renewal may begin in classrooms, communities and the local school board meetings shaping them. For journalists covering education, race or civic engagement, Bridgeforth offers data-driven insight, lived experience and policy expertise – helping make sense of one of the most pressing questions of our time: How can we build systems that truly serve all students and communities? This work collectively demonstrates a number of promising opportunities to foster more inclusive, community-connected forms of governance, particularly in a time of eroding trust in government institutions." – Bridgeforth ABOUT JAMES BRIDGEFORTH Assistant Professor, College of Education and Human Development James Bridgeforth is an educator, researcher and policy advocate whose work focuses on community voice in education policy and the politics of educational leadership. His scholarship has appeared in top journals including Journal of School Leadership, Education Policy Analysis Archives, Educational Evaluation and Policy Analysis and Educational Administration Quarterly, and he has contributed to Education Week and The Washington Post. A recipient of the National Academy of Education/Spencer Foundation Dissertation Fellowship, Bridgeforth holds a Ph.D. in Urban Education Policy from the University of Southern California, an M.Ed. in Educational Administration and Policy from the University of Georgia, and a B.A. in Political Science and Sociology from Georgia College & State University. Expert available for: Interviews on K–12 school governance, education policy and democracy Commentary on community voice and equity in education decision-making Analysis of youth civic engagement and participatory leadership To contact Bridgeforth, email mediarelations@udel.edu.

View all posts
Powered by