How Calendarloom works
A calendar is something people plan their lives around, so it is fair to ask where the dates on it come from. This page answers that — what computes what, which sources are used, and how the results are checked.
Everything is built in your browser
When you press download, no server draws your calendar. The page you see is laid out on your own device and captured into the PDF there, which is why the download is immediate, why it works offline once the page has loaded, and why the title you type never leaves your computer. There is no account system anywhere in the product — not a hidden one, none.
Month and day names: the platform's own locale data
Calendarloom does not keep its own tables of month and day names. They come from the internationalisation data built into your browser and operating system (CLDR, the Common Locale Data Repository — the same data your phone uses to format dates). That is why 58 languages are available at no translation cost, why Serbian comes out in correct Cyrillic, and why Hungarian dates run year-first: the conventions ride along with the data.
Public holidays: Nager.Date, with the observed dates
Holiday data comes from the Nager.Date public holiday database, which covers more than two hundred countries. Two properties of that data are worth knowing. It reports the officially observed date — when a holiday falls at a weekend and the day off moves, the moved date is what you get. And it marks holidays that apply only to some regions, which Calendarloom labels rather than hides.
For the thirty-five countries with their own pages the data is baked into the site at build time, covering 2025 to 2030, so those calendars do not depend on a third party being reachable. The picker offers over two hundred countries, and choosing one of the others asks Nager.Date directly from your browser — which means your IP address reaches them, as the privacy notice sets out.
Moon phases: Meeus, with the ΔT correction
Phases are computed with the algorithms from Jean Meeus's Astronomical Algorithms(chapter 49), including the ΔT correction for the drift between Terrestrial Time and UTC — about 70 seconds today, several minutes by 2100. Without it, any phase falling near midnight lands on the wrong calendar day.
The implementation is tested against an independent source: all 213 published perigee full moons ("supermoons") between 2001 and 2100 must come back as full moons on the same calendar day, and the build's test suite asserts exactly that. The one mismatch ever found — a full moon at 23:59 — is what led to the ΔT correction being added.
Sunrise, moonrise and the solunar index
The daily planner's sun and moon times are computed with the astronomy-engine library for the location you choose, and formatted in that place's own time zone — a New York sunrise reads 06:17 whether you print it in New York or Budapest. The solunar fishing periods follow the classical rule set: major periods around the moon's transit and anti-transit, minors around moonrise and moonset, rated by the moon's age. The garden and lifestyle sections print long-standing folk tradition and are labelled as such on the sheet.
Why the PDF is an image
The page is placed into the PDF as a high-resolution raster (about 288 DPI at print size) rather than as text with embedded fonts. The trade is explicit: text in the file cannot be selected or searched, and in exchange every writing system prints exactly as rendered — Latin, Cyrillic, Turkish dotless ı — with no font embedding to go wrong on the printing computer. For a document whose purpose is paper, we take that trade.
Who is behind it
Calendarloom is operated by Epacta Bt., a Hungarian company — full details on the imprint page. The product is free, without a paid tier; the calendars you generate are yours, commercial use included, as the terms spell out. What the site does and does not do with data is in the privacy notice. The short version: what you write on a calendar or planner stays on your device, and analytics only runs if you allow it. What does go out is listed there in full — the holiday list for the country you pick, and a place name if you use the planner's location search.