The Hanke-Henry Permanent Calendar would replace the Gregorian calendar with a simpler, permanent system in which every year is identical and every date always falls on the same day of the week. Professor Hanke and Professor Richard Conn Henry (JHU Physics & Astronomy) have collaborated on this proposal since approximately 2004.
The Problem with the Gregorian Calendar
The Gregorian calendar — in use since 1582 — has a fundamental flaw: no two years are alike. January 1st falls on a different day of the week each year. Holidays drift. Quarters have different numbers of days. The calendar that governs global commerce, finance, and daily life is needlessly irregular.
This creates real economic costs:
- Financial calculations must account for varying quarter lengths
- Business comparisons across years are complicated by shifting day-of-week patterns
- Scheduling recurrence (e.g., "the third Tuesday of every month") becomes complex across years
- International coordination is hampered by the unpredictability of the calendar
The Hanke-Henry Solution
Every year is identical. Every date always falls on the same day of the week.
The Hanke-Henry Permanent Calendar achieves this through a simple but elegant structural reform:
The year is divided into four three-month quarters. Each month begins on the same day and date each year. The first two months of each quarter are made up of 30 days, and the third is made up of 31 days. Each quarter contains the same number of days. Each quarter contains 91 days, resulting in a 364-day year that is comprised of 52 seven-day weeks. This is a vital feature of the HHPC because, by preserving the seven-day Sabbath cycle, the HHPC abides by the fourth commandment.
Core Features
Feature | Detail |
Identical years | Every year has the same structure — same months, same days |
Fixed day-of-week | Every calendar date falls on the same day of the week, every year, forever |
52 weeks = 364 days | The base year has exactly 364 days (52 × 7) |
Extra week | One "extra week" (Week 53 — Hanke-Henry Extra Week, or "Xtr") is inserted every 5–6 years to keep pace with the solar year |
Universal time | Time zones are abolished in favor of a single universal time |
7-day week preserved | The Sabbath and 7-day week cycle continue uninterrupted |
The "Extra Week" Mechanism
The solar year is approximately 365.24 days. A 364-day calendar falls short by about 1.24 days per year. To compensate, Hanke and Henry insert a full extra week (7 days) every 5–6 years — roughly when the accumulated deficit reaches 7 days.
This is analogous to the Gregorian calendar's leap day, but using a full week preserves the integrity of the 7-day weekly cycle. No date is ever orphaned from its weekday.
The Sabbath Question: No Religious Opposition
A critical design feature: The Hanke-Henry calendar deliberately preserves the 7-day week cycle without interruption. This means the Sabbath — whether observed on Friday, Saturday, or Sunday — continues to fall at its regular weekly interval.
Previous calendar reform proposals (such as the 13-month "International Fixed Calendar" and the "World Calendar") faced fierce opposition from religious groups because they required inserting "blank days" outside the weekly cycle — days that were neither a weekday nor a weekday in the next week. This disrupted the Sabbath cycle.
The Hanke-Henry calendar avoids this entirely. Every day belongs to a week. The 7-day cycle is never broken. This is why the proposal has not attracted the religious criticism that sank earlier reform attempts.
Benefits
Economic and Financial
- Every quarter has exactly the same number of days (91 days = 13 weeks) — simplifying all quarterly financial calculations
- Year-over-year comparisons are perfectly consistent
- Interest calculations, depreciation schedules, and lease terms are simplified
- Business planning is easier when the calendar is fully predictable
Practical and Social
- Holidays and anniversaries always fall on the same day of the week
- School years, sports seasons, and recurring events need never be re-scheduled
- "What day is March 15th this year?" has a permanent, unchanging answer
International Coordination
- Universal time eliminates the confusion of time zones for global commerce
- A single, invariant calendar reduces friction in international scheduling
Time and Time Zones
Before time was standardized, every city kept its own solar time, once called “true time.” In the early 19th century, the U.S. had more than 300 “sun zones.” Railways forced standardization: by 1875 there were 75 different railway times, including three in Chicago and six in St. Louis. Scheduling was chaotic, passengers were confused, and railroad accidents were sometimes fatal. Standard Railway Time introduced today’s time zones in 1883, and the Standard Time Act of 1918 wrote them into law.
Professor Hanke’s proposal: Scrap time zones and put the whole country on Coordinated Universal Time (UTC). Every clock in the U.S. would show the same time. What changes from place to place is the hour the sun is highest in the sky:
- New York: midday would be 17:00 UTC. A 9-to-5 workday would run from 14:00 to 22:00 UTC.
- San Francisco: midday would be 20:00 UTC. A 9-to-5 workday would run from 17:00 to 01:00 UTC.
Nobody would go to work in the dark. Business hours would simply be set in UTC.
Why it matters:
- A return to “true time.” People would rise with the sun and sleep when it’s dark, in line with their circadian rhythms. That would end social jet lag and its health effects.
- UTC is already the standard. Pilots use it for safety. Global stock and commodity trades are time-stamped in UTC. The internet and GPS run on it. In Professor Hanke’s words, UTC is already “the thread that ties most of the global economy together.”
Recent Publications (2025–2026)
- Three Solutions to the Time-Change Debate — Op-ed, WSJ