Enter Any Date
Keys: ← → a day, Shift + arrows a week, ↑ ↓ a month, PgUp PgDn a year, T today.
Step and Sweep
Today on the Wall
Computing the wall for your local date
Day numbers
- R.D.
- —
- JDN
- —
- MJD
- —
- Unix
- —
Fixed day (rata die) counted from Monday 1 January 1; the Julian Day Number at noon UTC; seconds at 00:00 UTC
Computing fifteen calendars: the Sun and the Moon take a moment.
The Year in Overlay
Twelve civil months with each day's Hebrew, Islamic and Chinese day numbers set small, and the moveable feasts in red. Pick a day to put it on the wall.
feast (hover or focus for its name) the day on the wall today by your device's clock
No overlays: switch Hebrew, Islamic or Chinese back on to see their day numbers under each civil day.
Moveable Feasts
Every feast in the civil year, with its distance from the day on the wall.
| Feast | Date | Distance | Begins | Note |
|---|
How It Is Computed
Every date on the wall is one integer first. R.D. 1 is Monday, 1 January 1 in the proleptic Gregorian calendar, and each calendar is a pair of functions between its own year, month and day and that fixed day. The arithmetic calendars (Gregorian, Julian, Hebrew, tabular Islamic, Coptic, Ethiopic, Armenian, the Romme and 33-year variants, the Mayan counts) need nothing but integer division. The Persian, Badí', French Republican and Chinese calendars are astronomical: they ask where the Sun and the Moon were, so the page carries the Sun's apparent longitude from a 49-term series, new moons from Meeus's chapter 49, the Moon's position from the chapter 47 series, the equation of time, sidereal time, sunset and moonset, and ΔT from a polynomial fit.
The rules are the ones the books print: Reingold and Dershowitz for every calendar, Meeus for the sky. The code is this page's own. Where the rule turns on a margin, the plate says what the margin was: the Persian year waits for the equinox before true noon at 52.5° E, the Badí' year for the equinox before sunset at Tehran, the Republican year for the true autumnal equinox at Paris, the Chinese month for the new moon on the 120° E civil day.
The Receipts
The test suite pins known dates and worked examples. A pinned miss stays pinned; nothing was loosened to pass.
| Receipt | Expected | Verdict |
|---|---|---|
| R.D. 1, JDN 2451545, Unix epoch R.D. 719163 | by definition | pass |
| 2000-01-01 in Hebrew, Islamic, Persian, Coptic, Ethiopic, ISO, Mayan | 23 Tevet 5760 · 24 Ramadan 1420 · 11 Dey 1378 · 22 Koiak 1716 · 22 Tahsas 1992 · 1999-W52-6 · 12.19.6.15.2 | pass |
| Gregorian Easter 1818–2038, two routes | Meeus/Jones/Butcher = paschal moon, 1583–3000 | pass |
| Rosh Hashanah, Pesach, Hanukkah 5786–5787 | 2025-09-23 · 2026-04-02 · 2025-12-15 · 2026-09-12 | pass |
| Chinese New Year 2025, 2026, 2027; leap 6th month of 2025 | 01-29 Snake · 02-17 Horse · 02-06 Goat | pass |
| Nowruz 1404, 1405 | 2025-03-21 · 2026-03-21 | pass |
| Meeus 25.a, 47.a, 49.a; equinox 2026-03-20 14:46 UTC | 199.90° · λ 133.167° · 1977-02-18 03:37 TD · within 2 min | pass |
| Umm al-Qura 1 Muharram 1447 | 2025-06-26 (tabular: 06-27) | pass |
| Hebrew year 5784 length | brief said 385; two routes say 383 | disputed, pinned 383 |
| Naw-Rúz 2026 | published 03-21; computed 03-20, margin 44 s | disputed, pinned |
What It Does Not Know
- Hindu calendars. Out of scope here. The lunisolar and solar Hindu calendars need true lunar days and true solar months, and deserve a page of their own.
- Sighting. The Islamic date is the tabular one, labelled so every time. The Umm al-Qura line is an approximation from the Mecca criterion with a truncated lunar theory; a calendar fixed by sighting can differ from both by a day.
- The last minute. Where an equinox and a sunset fall within a minute of each other, as they do at Tehran on 20 March 2026, this astronomy cannot decide the year; the plate says so and the published tables govern.
- Deep time. Before about 1000 and after 3000 every rule here is an extrapolation. Nobody wrote 1 January 1 on that day, and ΔT is a fit, not a record.
- Your clock. The page starts from the calendar date your device reports. A Hebrew, Islamic or Badí' day began at the previous sunset, and each of those plates says so.
- The Republican day names. The 360 rural names (Raisin, Safran, …) are not carried; the décade names and the complementary days are.
On Your Home Screen
Add the page to your home screen and it opens like an app, offline. Nothing is stored except the files of the page itself.