📅 The Hanke-Henry Permanent Calendar proposes to 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:
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
The Collaboration: Hanke and Henry
Professor Richard Conn Henry is a professor in the Johns Hopkins Department of Physics and Astronomy, known for his work in astrophysics and his advocacy for calendar reform. The Hanke-Henry collaboration brings together:
- Henry's expertise in astronomy and the mathematics of time measurement
- Hanke's economic analysis of the costs of calendar irregularity and the benefits of reform
The calendar has been published and promoted through the Johns Hopkins community and has attracted attention from calendar reform advocates worldwide.
A Window Into Hanke's Intellectual Range
The Hanke-Henry Permanent Calendar is a minor but fascinating side project that illustrates the breadth of Professor Hanke's intellectual curiosity. It applies the same economic logic that drives his work on currency boards — rules-based systems are more efficient and predictable than discretionary ones — to the most fundamental scheduling institution in human civilization.
In Hanke's view, the Gregorian calendar is a legacy system with unnecessary complexity — much like a discretionary central bank. Both could be replaced by simpler, more predictable, rules-based alternatives with significant economic benefits.
Recent Publications (2025–2026)
- Three Solutions to the Time-Change Debate — Op-ed, WSJ