Calendar Converter (Gregorian/Julian/Hebrew/Islamic)
Convert dates between Gregorian, Julian, Hebrew, and Islamic calendars with Julian Day Numbers. Essential for working with historical documents.
Unpublished research on cloud servers is a leak waiting to happen
The Historian's Knife is the answer
Grant applications. Unpublished findings. Peer review drafts. Novel methodologies. Cloud tools expose your intellectual property before you're ready. Analyse, synthesise, and write locally. Your research stays yours until you decide to publish.
The Historian's Knife is a single-file knife with 5 tools that runs entirely in your browser. The Historian's Knife puts five essential history and genealogy tools into a single HTML file. Convert dates between Gregorian, Julian, Hebrew, and Islamic calendars with Julian Day Numbers, convert Roman numerals in both directions with full reference tables, explore ancient numeral systems including Babylonian, Egyptian, and Mayan, look up regnal years for English and French monarchs, and compute Soundex codes for genealogical name matching — all offline, all private, all yours forever.
WHAT'S INSIDE
5 tools in a single HTML file
Roman Numeral Converter
Convert between Roman numerals and Arabic numbers in both directions. Includes a reference table and handles values up to 3,999,999.
Ancient Numeral Systems
Explore Babylonian sexagesimal, Egyptian hieroglyphic, Mayan vigesimal, and other ancient number systems with interactive conversion.
Regnal Year Calculator
Look up regnal years for English and French monarchs — convert between regnal dates (e.g., '3 Henry VIII') and calendar dates.
HOW IT WORKS
Three steps. No setup.
1
Download the file
Purchase The Historian's Knife and download a single HTML file. No installer, no account, no setup.
2
Open in any browser
Double-click to open in Chrome, Firefox, Safari, or Edge. Works on any operating system.
3
Start working
Your data stays in your browser's local storage. Nothing is uploaded. Ever.
COMPLIANCE & GEOGRAPHY
Global
Works in any country. No server dependency, no regional restrictions.
FAQ
Frequently Asked Questions
How does The Historian's Knife solve the research integrity problem?
The Historian's Knife runs entirely in your browser. Grant applications. Unpublished findings. Peer review drafts. Novel methodologies. Cloud tools expose your intellectual property before you're ready. Analyse, synthesise, and write locally. Your research stays yours until you decide to publish. Calendar converter (Gregorian, Julian, Hebrew, Islamic), Roman numeral converter, ancient numeral systems, regnal year calculator, and genealogy Soundex. Your archive in a file.
Is my data safe with The Historian's Knife?
Yes. The Historian's Knife is a single HTML file. It never connects to any server. Your data stays in your browser's local storage on your device.
What makes The Historian's Knife different from cloud tools?
Cloud tools require internet, charge subscriptions, and store your data externally. The Historian's Knife is a one-time purchase ($39), works offline, and never transmits data.
Is The Historian's Knife really just one file?
Yes. The Historian's Knife is a single HTML file containing 5 tools. Download it, open it in any browser, and start working. No installation, no dependencies, no accounts.
No cloud One fileOne-time purchase
Get The Historian's Knife — $39Sovereignty as a Service