About On This Day
One historical event, examined in depth, for every day of the year.
On This Day — A Deep-Dive Almanac is a perpetual almanac of history. For each day of the calendar year, it offers an original, sourced deep-dive into a single event that happened on that date. It currently holds 21 entries spanning 20 days, drawing on 55 distinct sources.
How it is made
Entries are built from human-vetted facts, each tied to a citation. Where a draft is assisted by a language model, the model is constrained to write prose only from the supplied, sourced facts — it is never asked to invent dates, names, or numbers. The result is then reviewed before publication. Every entry lists its sources and carries a confidence rating.
Frequently asked
What is On This Day?
A perpetual almanac. Each calendar day has a deep-dive on a single historical event that happened on that date, with every claim backed by cited sources.
Are the entries written by AI?
Some drafts are assisted by a large language model working strictly from human-vetted, sourced facts — never from the model’s unaided memory. Each entry carries a confidence rating and, where relevant, an "AI-assisted draft" badge, and every entry lists its sources so you can check the record yourself.
How do you handle uncertainty?
History is reconstructed from imperfect records. Every entry carries a confidence rating (high, medium, or low) and cites its sources. We would rather flag uncertainty than hide it.
I found an error. How do I report it?
Email [email protected] with the entry and the correction. Sourced corrections are very welcome.
Get involved
Spotted a mistake or have a better source? Email [email protected]. Browse the perpetual calendar or the full archive to start reading.