Would you want your doctor using medical information from the early 1900s to diagnose and treat your most recent malady? Probably not. What about scientists evaluating 150 years worth of data documenting glacial decline in Iceland? The use of historical data is certainly needed here!
When thinking about currency, think about your information need in context.
Start with your project's prompt: Does it speciify a specific date range that you must consult? If not, you can always reach out to your instructor for feedback on the best date range to use in your research.
After reading your assignment's details, begin doing some preliminary searches on your topic. At this stage, search broadly and be on the lookout for publication dates. Many databases provide a date slider or date bar graph that provides a snapshot of publication dates. Is current research available on your topic, or did research on this topic peak in previous decades?
Having a general sense of publication dates can help inform your searching. Some projects might need to be limited to the past 3 years, while others might span a 30 year date window.
"Seminal literature," also referred to as pivotal or landmark studies, are the foundational works that first provided novel information and ideas in a particular discipline. Seminal works are highly cited in the literature, so you will likely encounter the same work (i.e. citation) numerous times throughout a research project.
An example of a seminal work is the 1904 book published by Marie Curie, Recherches sur les Substances Radioactives (trans. Research on Radioactive Substances). Curie's research led to huge advances in the chemical, physical, and medical sciences.
It is important to note that seminal works are usually older, as they have been cited and consulted for many years. Because seminal sources are older, if limiting by date, you may not see these results in your search, or your may unknowingly exclude a seminal source all together.
Including seminal works is a great way to highlight just how far research has come in a specific domain. Talk with your instructor to learn more about using seminal works in your research. If you need help finding seminal literature, reach out to your liaison librarian.
M0002559 Portrait of Marie Curie [1867-1934], Polish Chemist, Wellcome Library, London. CC BY-4.0