--- type: Documentation title: Publication dates in Librario description: Which notations the publication date accepts, from 2020 to circa 1975 and 1985–1992, how Librario shows them in words and how search finds them. resource: https://www.librario.de/en/docs/grundlagen/veroeffentlichungsdaten language: en revision: 32aa58bd8c6656a8a37324453689bbe77825d242 tags: - docs - grundlagen --- # Publication dates in Librario Not every work has an exact publication date. An old paperback says only “around 1975”, a multi-volume work appeared from 1973 to 1986, a journal issue came out in spring 2004. Librario takes such dates in the **Publication date** field and shows them in words: on the publication page, in the search results and in shared links. The notations follow the open EDTF standard of the Library of Congress. The same notation works for cataloguing and for the **Year** filter in search. ## Notations | Kind of date | You write | Librario shows | | ------------------------- | ----------------- | ---------------------- | | Year | `2020` | 2020 | | Month | `2020-06` | June 2020 | | Day | `2020-06-15` | June 15, 2020 | | Decade | `197X` | 1970s | | Century | `19XX` | 1900–1999 | | Season | `2004-21` | Spring 2004 | | Period | `1985/1992` | 1985–1992 | | Period in months | `2004-03/2004-06` | March–June 2004 | | Open end | `2020/..` | 2020 onwards | | Open start | `../1990` | up to 1990 | | Approximate | `1975~` | circa 1975 | | Uncertain | `1975?` | 1975 (uncertain) | | Approximate and uncertain | `1975%` | circa 1975 (uncertain) | The seasons are `21` spring, `22` summer, `23` autumn and `24` winter. Winter runs from December into February of the following year, so Librario shows `2004-24` as “Winter 2004/05”. A period needs an exact date at both ends. Write `1970/1989` instead of `197X/198X`, and leave `~` and `?` off the ends. In the form, you don’t need to know the notation by heart. **Date helper…** next to the field opens **Enter publication date**. There you choose **Publication date**, **Date range** or **Decade or century**, and for a publication date also **Approximate (circa)** or **Uncertain (?)**. **Apply** writes the notation into the field. Under the field, Librario says in words what the date means, such as “circa 1975”. Type seasons directly, as in the table above. ![The Enter publication date dialog, in German, with the tabs Publication date, Date range and Decade or century. Publication date is selected with the year 1975 and Approximate (circa); the preview reads "ca. 1975", and the field will show 1975~.](/de/docs/grundlagen/veroeffentlichungsdaten/datumshilfe-formular.webp) _The date helper builds the notation 1975~ from the year and the precision Screenshot of the German interface._ Librario does not accept years before the Common Era. It also rejects rare EDTF forms such as `1XXX` or a mark on the month alone (`2004-?06`), and lists notations that work. ## Approximate and uncertain dates - **`~` approximate:** the year is an estimate, for example from the typography or a publisher’s list. Librario shows “circa 1975”. - **`?` uncertain:** the year is likely but not confirmed. Librario shows “1975 (uncertain)”. - **`%` both:** estimated and not confirmed. Librario shows “circa 1975 (uncertain)”. These marks change only how the date is shown, not how search finds it: search treats `1975~` like `1975`. ## How search finds a date The search results and the publication page show the date in words, such as “1970s” or “1973–1986”. **Search counts the earliest day of that date: 1 January 1970 for “1970s”, 1 January 1973 for “1973–1986”.** A filter finds the publication when that day falls inside the chosen period. So choose a period that includes the year the date begins with: for a work from the 1970s, drag the left handle to 1970 or earlier. | Recorded | Counts in search as | Found with | Not found with | | ----------- | ------------------- | ----------------------------- | ---------------- | | `2020` | 1 January 2020 | `2020`, `2015/..` | `2020-06` | | `197X` | 1 January 1970 | `1970`, `197X`, `1965/1975` | `1975` | | `1973/1986` | 1 January 1973 | `1973`, `1970/1979` | `1980/1989` | | `1975~` | 1 January 1975 | `1975`, `1970/1979` | `1974`, `1976` | | `2004-21` | 1 March 2004 | `2004`, `2004-03` | `2004-04` | | `../1990` | 1 January 1990 | `1990`, `1985/1995` | `1980` | An open start such as `../1990` has no earliest day, so the end counts instead. You choose the period in the chart above the **Year** filter, with a preset period or through **Choose period…**. [Searching for publications](/en/docs/grundlagen/publikationen-durchsuchen#zeitraum) shows how. The chart counts each publication in the year search finds it under. If many works are recorded as `197X`, the bar for 1970 stands out for that reason. Two notations exist only in search: - **Several dates:** `[1667,1668]` finds publications from 1667 or 1668. You cannot catalogue “1667 or 1668”. Record the period `1667/1668` instead; search then finds the work through 1667. - **No date:** `(null)` finds publications without a publication date. In **Choose period…** this is **No year specified**. ## Exports and interfaces Formats with a plain year field get the earliest possible year: `197X` becomes 1970, `19XX` 1900, `../1990` 1990. This applies to the year in BibTeX, EndNote and the CSV column “Publication year”. The full date sits alongside in the CSV column “Publication date”; BibLaTeX writes dates such as `197X` or `1973/1986` in full to the `date` field. The [data model](/en/docs/grundlagen/datenmodell#surfaces) describes what the AI assistant and the REST API return.