Help
Initially, the main area contains one timeline, with ticks representing evenly spaced points in time. A square represents a min or max date. '1k BC' means 1000 BC. 'mya' and 'bya' mean millions and billions of years ago.
Events are shown as labelled images. Blue borders indicate discovery events. This is so that events like the discovery of Andromeda don't look the same as the event of its creation.
Events are linked to points on the timeline that match their 'start date'. For a person, this is a date of birth. For a book, this is a date of publication. A dashed line indicates imprecision. {{touchDevice ? 'Tap' : 'Click'}} on an event to bring up more details.
The timeline also has varying 'thickness', which indicates how many events are present between ticks. There are four levels, indicating counts of zero to over a thousand.
The + button at the top right adds another timeline, if there's enough space.
The bar at the {{vert ? 'right' : 'bottom'}} represents the full range of possible dates. Each timeline's bounds are displayed as a yellow subregion. Timelines will often look very thin, as the whole bar spans billions of years.
Keyboard Shortcuts
- {{vert ? 'Up': 'Left'}} and {{vert ? 'Down': 'Right'}} pan the timeline
- Shift-{{vert ? 'Left' : 'Up'}} and Shift-{{vert ? 'Right' : 'Down'}} zoom in and out
- Plus and Delete add and remove timelines
- {{vert ? 'Left' : 'Up'}} and {{vert ? 'Right' : 'Down'}} switch between timelines
- Ctrl-F opens the search bar
- Esc closes an open pane
Settings
-
Categories
Allows filtering of displayed events by category. Examples include:
- Event: wars, disasters, celebrations
- Place: cities, countries, galaxies
- Person: writers, scientists, leaders
- Organism: dinosaurs, insects, plants
- Work: books, movies, video games
- Discovery: inventions, ideas, places
(Unfortunately, timeline thickness isn't yet indicative of filtered events)
-
Display
- Only events with images: If enabled, only about 20% of events are shown
- Minor tick text: Toggles labels for small-sized ticks
- Event density: Toggles timeline thickness
- Event lines: Toggles lines linking events to timelines
- Baseline: Toggles the bar representing the full date range
-
Input
- Pan ratio: Higher values mean faster panning
- Zoom ratio: Higher values mean faster zooming
{{touchDevice ? 'Tapping' : 'Clicking'}} on a slider's label resets it to its default value.
Chrona's source code is available from a self-hosted Git repository, under the MIT Licence.
Data Sources
- Event data was obtained from the Wikidata dump for 23/08/22. About 350,000 events were extracted.
- Event descriptions, images, and popularity were obtained via the Wikimedia dump for 01/05/22. Wikipedia page content is available under CC BY-SA 3.0. For the source of a specific event's image, look in its info pane.
Other Credits
- The UI was mostly coded in Typescript, and built wth Vue, Vite & Pinia
- Tree data was processed using Python, and stored using Sqlite
- Styling was enhanced using Tailwind
- The font is Ubuntu Font, licensed under Ubuntu font licence
- Icons were used from Feathericons and Ionicons, both under MIT License
- Images were cropped using Smartcrop
How accurate is the information?
Event data was extracted by looking for objects in the Wikidata knowledge graph that have certain properties. These are not always consistent or accurate. For example, an event's date might be encoded using a 'start time', 'temporal range start', or 'earliest date' property, without a clear pattern.
Also, some properties have unclear definitions. For example, in looking for creative works, a 'genre' property was used. But as it turns out, sometimes fictional characters or places will also have that property, which can cause unexpected results (like having Hogwarts displayed as a work).
As for the short descriptions, they were extracted from marked-up Wikipedia content using imprecise heuristics. Many have leftover fragments of code, or incomplete sentences.
In the info boxes, what do terms like "1st century BC" and "O.S." mean?
Each event can have both a start and end date, both of which may be imprecise. For example, the start may range between years 1901 and 2000, which corresponds to the 20th century. Similarly, the 1st century BC represents years 99 BC to 1 BC. There is no year 0 BC, because 1 BC is directly followed by 1 AD.
Decades are like centuries, and have ranges like 1701 to 1710, generally ranging from a year ending with one up to a year ending with zero. Other scales are different. "2nd millenium" means 1000 to 1999. And "About 2 million years ago" means 2,000,000 BC to 1,000,001 BC.
For dates like "1st Jan 1600 (O.S.)", the "O.S." means Old Style, and the date is in the Julian Calendar (as opposed to the Gregorian Calendar). These tend to appear for events in certain countries between 1550 and 1950.
Why am I sometimes unable to zoom into a year?
Calendar dates are only valid starting from the year {{-MIN_CAL_YEAR}} BC. This is because Julian day numbers are used to encode calendar dates. Before this point, zooming into sub-yearly scales is disabled.
Why are there so many celebrities?
Events are chosen for display by popularity, which is determined using Wikipedia page view counts. Celebrities tend to rank highly with this metric, regardless of historical importance. This might be adjusted in future.
Why do some people have their faces clipped out?
Images from Wikipedia were cropped into squares semi-automatically. This sometimes ends badly, with the person's chest or headwear being placed in center focus.
Last updated 28/01/23