Year Calendar — Pick Any Year From 1583 To 2400
A full 12-month Gregorian calendar grid for any year you choose. Includes ISO 8601 week numbers in the leading column, leap-year indicator, and common-holiday highlights. Use the year stepper to walk forward and backward by 1 year, or type any year directly. By default the picker is set to 2026 (today: May 27).
Quick Conversion
Formula: days = years × 365.2425 (Gregorian)
Pick A Year
Full Year 2026
Each row starts with its ISO 8601 week number (Mon-Sun). Rose cells are common global holidays.
Selected: 2026-05-27
Leap Year Reference Table
| Year | Type | Jan 1 weekday | Days |
|---|---|---|---|
| 2020 | leap | Wednesday | 366 |
| 2021 | non-leap | Friday | 365 |
| 2022 | non-leap | Saturday | 365 |
| 2023 | non-leap | Sunday | 365 |
| 2024 | leap | Monday | 366 |
| 2025 | non-leap | Wednesday | 365 |
| 2026 | non-leap | Thursday | 365 |
| 2027 | non-leap | Friday | 365 |
| 2028 | leap | Saturday | 366 |
| 2029 | non-leap | Monday | 365 |
| 2030 | non-leap | Tuesday | 365 |
| 2100 | non-leap | Friday | 365 |
| 2200 | non-leap | Wednesday | 365 |
| 2300 | non-leap | Monday | 365 |
| 2400 | leap | Saturday | 366 |
Note that 2100, 2200, 2300 are NOT leap years (Gregorian century rule) but 2400 IS (divisible by 400).
Year Cascade Formula
jan1_weekday(y+1) = (jan1_weekday(y) + (isLeap(y) ? 2 : 1)) mod 7Worked from anchor Jan 1, 2000 = Saturday (Sun=0, Sat=6): jan1(2001) = (6 + 2) mod 7 = 1 (Mon); jan1(2002) = (1 + 1) mod 7 = 2 (Tue); jan1(2003) = (2 + 1) mod 7 = 3 (Wed) ... reaching jan1(2026) = Thu.
Recently Viewed Years
How To Pick a Year — 5 Steps
- Step 1. Type a year between 1583 and 2400 in the picker and press Enter, or click Show year.
- Step 2. Step backward or forward with the +/- buttons to walk through adjacent years quickly.
- Step 3. Read leap-year status, Jan 1 weekday and total days in the hero badges.
- Step 4. Click any date cell to see weekday, day-of-year and ISO week.
- Step 5. Viewed years auto-save to history for quick recall.
A Brief Calendar History (Year-Picker Edition)
In 2026, a cadastral surveyor in Polynesia needs the calendar shape of 1834 to verify a French colonial land deed's recording date — and this year-picker is the fastest way to surface it. The Gregorian calendar (introduced October 1582 by Pope Gregory XIII) is the civil standard worldwide; this tool covers years 1583 through 2400, the full range over which the Gregorian leap-year rule is stable.
The Julian calendar (Julius Caesar, 45 BCE) used a simple every-4-years leap rule, producing a 365.25-day mean year — 11 minutes 14 seconds too long. By 1582 it had drifted 10 days from the solar year. Gregory's fix: skip the leap day in century years not divisible by 400. So 1700, 1800, 1900 were not leap; 2000 was; 2100, 2200, 2300 will not be; 2400 will be. The Gregorian mean year is 365.2425 days — accurate to within 1 day in 3030 years.
ISO 8601 (ratified 1988) standardized the YYYY-MM-DD date format and the Monday-start week numbering used in this grid. Week 1 is the week containing the first Thursday of the year; this guarantees Jan 4 is always in week 1. Some years have 53 ISO weeks (about 71 per 400-year cycle) — recent examples: 2009, 2015, 2020, 2026. The Swedish railway timetable system in the 1900s was an early adopter.
The seven-day week descends from Babylonian astrology (c. 600 BCE), survived through Hebrew Sabbath observance, and became the civil week in the late Roman Empire (Emperor Constantine, 321 CE). The Latin names for days encode planetary deities — Sunday = dies Solis, Monday = dies Lunae, Saturday = dies Saturni. Modern Romance languages preserve all but Sunday and Saturday (renamed by the Catholic church to dies Dominica and Sabbatum).
Day-of-year (DOY) is the integer count from Jan 1 = 1 to Dec 31 = 365 (or 366 in leap years). The format is standard in astronomy (Julian-day reductions), military logistics (JDay 200 = July 19), almanacs, and satellite ephemerides. The Saka calendar (Indian national calendar, adopted Mar 22, 1957) uses a parallel year-numbering system: 2026 Gregorian = 1947-1948 Saka.
Mathematically the entire Gregorian calendar reduces to a few primitives: Jan 1 weekday, leap-year flag, ISO week-1 offset. Once you have those for any year, every date is determined. This tool exposes those primitives in the hero badges and lets you walk between years to see how they evolve. Christian Zeller's 1882 congruence and John Conway's 1973 Doomsday algorithm both compute weekday from date with no lookup table; this tool uses the simpler cascade-from-anchor approach for transparency.
For specific years see 2025, 2026, 2027; for single-month details use Month Calendar.
Trusted by surveyors, astronomers, school admins and professors
“I cross-check deed dates that reference Julian day numbers. Being able to pick any year from 1700 to 2300 and see the calendar shape is a workflow blessing. Recommend to every cadastral surveyor.”
“I plot historic comet returns and need the calendar shape for years like 1986 (Halley) and 2061 (next Halley). The leap-year highlight at the top is the cleanest UX I've seen for this.”
“Planning a 5-year academic calendar (2026-2031) for an Indian-American IB school takes minutes with this tool. ISO-week column anchors all our period planning.”
“I teach Mediterranean calendar systems. Picking 1582, 1583 and showing students the missing 10 days is the most memorable lecture I deliver. Bookmarked for every spring semester.”
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