How recent your sources should be depends on two things: what your brief says, and how fast your field moves. APA Style, which most nursing and psychology students use, has no year cut-off at all, while some nursing programmes require every scholarly source to be from the last five years. The limit, where there is one, is set by the course, not the style.
EdCitation publishes this guide, drawn from the APA Style blog, library guides at eight universities and colleges, the Cochrane Handbook and one study, all read on 27 September 2026 and dated by their own "last updated" lines. Where a guide states a rule, it is quoted; where none does, we say so.
EdCitation can do two of these steps for you, free and without an account. Check your paper reads the date rule out of your brief, and the Year published filter in Find sources keeps a search to the years the brief allows.
Is there a rule on how old sources can be?
No general rule exists: the limit is whatever your brief or course sets. Greenbaum (2021), on the APA Style blog, files the belief that sources must date from the last 5 to 10 years under myths, and is blunt about it: "APA Style has no year-related cutoff". The same post says to follow an instructor who sets a time frame.
Where a course sets a limit, it is written into the assignment. The Shapiro Library at Southern New Hampshire University (2026b) tells students to look in the rubric for wording like "sources must be published in the last 5 years", and to fall back on the field's norms only when the assignment says nothing.
Where the guides disagree
Hallmark University (2026) tells its students that "APA typically recommends using sources published within the last 5-10 years" unless a work is seminal. APA's own blog says the opposite, and on what APA requires, the style's publisher wins. The practical answer is the same everywhere: the style sets no limit, your brief may, and the brief is what is marked. How many sources to use is a separate question, covered in how many references a paper needs.
Why do assignment briefs set a date limit?
Briefs set a date limit because evidence changes, and a paper built on old findings can recommend what is no longer done. Health research has measured it. Shojania et al. (2007) followed 100 systematic reviews of drugs, devices and procedures: the median time before new evidence signalled a need to update was 5.5 years, the signal came within two years for 23%, and for 7% it had come before the review was published.
The Cochrane Handbook says the same of its own reviews: as new studies finish, a review can go out of date and mislead the people relying on it (Cumpston & Flemyng, 2023). A date limit makes sure you read the evidence as it stands now.
How recent should references be in nursing?
In nursing and health, the common rule is the last five years, and some programmes apply it to every scholarly source. Southern New Hampshire University's graduate nursing guide (n.d.) defines a current source as one "dated to within the last five years" and states that "all scholarly sources must be dated within the last five years". For professional sources, such as a clinical guideline, it asks for the last five years where possible and otherwise the most recent version available.
The same university's general FAQ suggests a tighter rule of thumb for fast-moving fields, naming health care and nursing: sources from the past two to three years (Southern New Hampshire University Shapiro Library, 2026b). That is a suggestion; your brief comes first.
Guidelines need their own check. Frontier Nursing University (2026) calls society guidelines often excellent but warns "often they have not been revised for quite some time", and says to add current research articles when a guideline is old.
How old can sources be in technology, law and history?
The acceptable age changes by subject, and the library guides say so directly.
Technology, engineering and the sciences
The sciences want the newest work. Williams College Libraries (2026) put it in one line: "science papers need up-to-the-minute information", while social studies can use work published years ago. Southern New Hampshire University (2026b) places engineering, business and education in its fast-paced group with health, under the two-to-three-year rule of thumb. We found no guide stating a separate number for computing, so we give none.
Law: whether it still stands, not how old it is
In law, the test is status, not age. The University of Cincinnati Libraries (2026) tell students to check a case's status with a citator, KeyCite on Westlaw or Shepard's on Lexis, and warn that a case marked with a red flag or red stop sign "may no longer be good law".
History and the humanities
Older sources are normal here. Williams College Libraries (2026) note that humanities papers often rely on sources decades or centuries old, and Southern New Hampshire University (2026b) names diaries and letters used as primary sources in history. Even so, its rule of thumb for the arts, humanities and history is sources from the past five years.
| Subject or institution | The rule it states | Source |
|---|---|---|
| APA Style | No time limit on sources; follow any limit your instructor sets | Greenbaum (2021) |
| Southern New Hampshire University, graduate nursing | Scholarly sources "must be dated within the last five years"; professional sources the most recent version available | Southern New Hampshire University Shapiro Library (n.d.) |
| Southern New Hampshire University, all subjects | Rule of thumb: past 5 years for arts, humanities and history; past 2 to 3 years for health, nursing, engineering, business and education | Southern New Hampshire University Shapiro Library (2026b) |
| Hallmark University | "within the last 5-10 years" unless seminal (APA's own blog disagrees) | Hallmark University (2026) |
| Frontier Nursing University | Check a guideline's date; add current research when it is old | Frontier Nursing University (2026) |
| Williams College | Sciences up to the minute; humanities decades or centuries old | Williams College Libraries (2026) |
| University of Cincinnati, law | Age is not the test; a case must still be good law | University of Cincinnati Libraries (2026) |
| College of Southern Maryland; MCPHS University | No date limit when searching for seminal works | College of Southern Maryland Libraries (2026); MCPHS University Library (2025) |
| EdCitation Find sources | Year published keeps a search to 1, 3, 5 or 10 years, or a range you type | Our run, below |
Can I use old sources in a literature review?
Yes, when the old source is a seminal work, and a literature review is expected to include the ones its field is built on. Greenbaum (2021) gives Bandura's 1961 Bobo doll study as a seminal paper still cited in current psychology. Hallmark University (2026) advises balancing older research with the most current studies: seminal works for where an idea came from, recent work for where it stands.
How to recognise a seminal work
A seminal work is one the field keeps citing. MCPHS University Library (2025) says it carries no "seminal" label; instead the same author and title keep turning up in reference lists. The College of Southern Maryland Libraries (2026) give the rule: "Do not use a date limiter when searching for seminal works in a database". A five-year filter hides the very papers you want.
A nursing example: Bergstrom et al. (1987) published the Braden Scale for predicting pressure sore risk, and when we searched for it in EdCitation's Find sources, its record showed it cited 1,159 times. Under a "last five years" brief, cite a 1987 paper only if the brief allows seminal works or your tutor agrees, with recent studies that use the scale beside it.
How do I find the newest evidence, or a later version of an old study?
Search with the date limit first, then check each older source for a newer version.
- Read the date rule in your brief word for word. Check your paper pulls it out with the sentence it came from.
- Search with the years allowed. In EdCitation's Find sources, set Year published or type the first year into the From box.
- Start from a recent review, which summarises the older studies and shows which still matter.
- For each older source you keep, search its title for an update. Systematic reviews are updated and republished (Cumpston & Flemyng, 2023), and an update may say so in its title, as Wu et al. (2022) did with "an updated systematic review".
- For a guideline, find the current edition on its publisher's own site and cite that.
- Build each reference in Cite a source, which screens it for retraction, then check the whole list in Verify references.
What if there is little recent research on my topic?
Say so, cite the best older work, and tell your tutor before the deadline. A thin recent literature is a finding in itself. The University of Louisiana Monroe Library (2026) describes gaps in the literature as areas unexplored, under-explored or outdated, and notes that finding no articles may indicate a gap. Southern New Hampshire University (2026a) counts outdated research as a gap, with 2001 studies of Internet use as its example.
Widen the search first: synonyms, a related population, a neighbouring discipline. If the limit still cannot be met honestly, ask whoever set it whether older work is acceptable, rather than padding the list with weak recent sources, and write the gap into the paper.
How do I filter sources by year in Find sources?
For a date rule, EdCitation's Find sources is the tool to reach for first: it searches about 300 million published works, applies the years before you read a title, and each result carries a Cite button that adds it to your reference list, looked up, never written. It is free, with no account. Year published offers five buttons, 1 yr, 3 yrs, 5 yrs, 10 yrs and Any, plus From and To boxes for an exact range. Two quick sets use it: "Journal articles, last 5 years" and "Published before 2022".
One detail matters. In 2026 the 5 yrs button sets the From year to 2021, so all of 2021 is included. If your brief counts differently, type the year it names into the From box.
One search, run four ways
On 27 September 2026 we ran pressure ulcer prevention. The main index was busy, so every run was answered by the back-up index, which reports any filter it cannot apply.
- No year range: 1,259,986 results. The first page held 95, dated 1996 to 2026; 16 were from 2021 or later and 5 had no year. First result: "Patients at Risk for Pressure Ulcers and Evidence-Based Care for Pressure Ulcer Prevention", Nancy Bergstorm (as the record spells it), Pressure Ulcer Research, no year.
- From 2021: 358,977 results, and all 93 on the first page dated 2021 to 2026. First result: "114 NI hospice pressure ulcer prevention group", Gillian Walker and Ken McMullan, Poster Presentations, 2025. No notice came back, so the range was applied.
- Published before 2022: 936,945 results, the first page dated 1994 to 2021.
- From 2021 with Free to read: the years held at 358,977, and the page reported "The full index is busy, so these filters are not applied right now: Open access."
A year filter does not choose the kind of source: add In a journal when the brief asks for journal articles.
Reading the date rule in your brief
The brief we tested is ours, written for this guide and not taken from any university, pasted into Check your paper. It asked for "at least 12 peer-reviewed sources published since 2015" and said "At least eight of your sources must be from the last five years."
The checklist read the first rule: Sources, "At least 12 sources", and Source dates, "2015 or later", each shown with the sentence it came from. The second sentence became no rule; it was listed under "What it asks you to do, which no rule can test", with the sentence allowing older seminal works. Count those yourself. Checking a finished paper against the checklist is Theoretics QA, in Max at $24 a month.
Citing the old and the new
Cite a source built both nursing papers from Crossref's records. From 10.3389/fpubh.2022.964680, in APA 7:
Wu, J., Wang, B., Zhu, L., & Jia, X. (2022). Nurses’ knowledge on pressure ulcer prevention: An updated systematic review and meta-analysis based on the Pressure Ulcer Knowledge Assessment Tool. Frontiers in Public Health, 10, Article 964680. https://doi.org/10.3389/fpubh.2022.964680
From 10.1097/00006199-198707000-00002, rerun on 27 September 2026:
Bergstrom, N., Braden, B. J., Laguzza, A., & Holman, V. (1987). The Braden scale for predicting pressure sore risk. Nursing Research, 36(4), 205–210. https://doi.org/10.1097/00006199-198707000-00002
The publisher's record stores the pages as "205???210", and the entry mends them to 205–210. The title is in sentence case, as APA asks; one fix by hand restores the scale's name, "The Braden Scale for predicting pressure sore risk". No retraction was reported for either. Both entries were looked up, not composed: EdCitation does not write a word of a student's paper. For the finished draft, the Pro tool References from a file, $8 a month, takes the whole document, looks up every entry and pairs each citation in the text with its reference.
Quick questions
Does APA require sources from the last five years?
No. APA's own blog says the style puts no time limit on sources. A five-year limit comes from your instructor or programme, and then it applies.
How recent should references be in nursing?
Often within the last five years, the rule Southern New Hampshire University's graduate nursing guide states for scholarly sources. Your own brief decides.
Can I use a source older than my brief allows?
Only if the brief allows seminal works or your tutor agrees. Cite recent studies beside it.
How do I find only recent sources?
Filter by date before reading. In EdCitation's free Find sources, choose 1, 3, 5 or 10 years under Year published, or type the first year your brief allows.
What counts as the last five years?
Courses count differently. A brief that names a year, such as "since 2015", is clear; if yours does not, ask which year to start from.
References
- Bergstrom, N., Braden, B. J., Laguzza, A., & Holman, V. (1987). The Braden Scale for predicting pressure sore risk. Nursing Research, 36(4), 205–210. https://doi.org/10.1097/00006199-198707000-00002
- College of Southern Maryland Libraries. (2026, April 6). Seminal works: Overview. https://libguides.csmd.edu/seminal
- Cumpston, M., & Flemyng, E. (2023). Chapter IV: Updating a review. In J. P. T. Higgins, J. Thomas, J. Chandler, M. Cumpston, T. Li, M. J. Page, & V. A. Welch (Eds.), Cochrane handbook for systematic reviews of interventions (Version 6.5). Cochrane. https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv
- Frontier Nursing University. (2026, June 24). Evaluating sources: Scholarly references. https://library.frontier.edu/c.php?g=143486&p=938038
- Greenbaum, H. (2021, October 18). The "outdated sources" myth. APA Style Blog. https://apastyle.apa.org/blog/outdated-sources-myth
- Hallmark University. (2026, September 14). APA Style, 7th edition: Current resources. https://hallmark.libguides.com/c.php?g=984470&p=10623133
- MCPHS University Library. (2025, August 18). Finding seminal research. https://mcphs.libguides.com/seminalresearch
- Shojania, K. G., Sampson, M., Ansari, M. T., Ji, J., Doucette, S., & Moher, D. (2007). How quickly do systematic reviews go out of date? A survival analysis. Annals of Internal Medicine, 147(4), 224–233. https://doi.org/10.7326/0003-4819-147-4-200708210-00179
- Southern New Hampshire University Shapiro Library. (n.d.). Nursing, graduate: Scholarly and professional sources. https://libguides.snhu.edu/MSN/scholarly
- Southern New Hampshire University Shapiro Library. (2026a, June 29). What is a research gap and how do I find one? https://libanswers.snhu.edu/faq/264001
- Southern New Hampshire University Shapiro Library. (2026b, August 24). How old should or can a source be for my research? https://libanswers.snhu.edu/faq/215024
- University of Cincinnati Libraries. (2026, August 19). Researching case law guide: Making sure cases are still good law. https://guides.libraries.uc.edu/c.php?g=222559&p=1472876
- University of Louisiana Monroe Library. (2026, September 22). Graduate education research guide: Gaps in the literature. https://ulm.libguides.com/c.php?g=1404063&p=10423114
- Williams College Libraries. (2026, August 25). Evaluating sources: Currency. https://libguides.williams.edu/evaluating-sources/currency
- Wu, J., Wang, B., Zhu, L., & Jia, X. (2022). Nurses' knowledge on pressure ulcer prevention: An updated systematic review and meta-analysis based on the Pressure Ulcer Knowledge Assessment Tool. Frontiers in Public Health, 10, Article 964680. https://doi.org/10.3389/fpubh.2022.964680