Hanke-Henry Permanent Calendar Converter

The Hanke-Henry Permanent Calendar (HHPC) is a proposed calendar reform by economists Steve Hanke and Richard Henry. It is a perpetual calendar where every date falls on the same day of the week every year — January 1 is always a Monday. It has 364 days in a normal year divided into 12 months across 4 equal quarters, with a 7-day 'Xtr' (Extra) leap week added approximately every 5 or 6 years.

Unlike the Gregorian calendar, where dates shift to different days of the week each year, the HHPC is permanent — every date is always the same weekday. The HHPC also eliminates the irregular month lengths of the Gregorian calendar; each quarter has months of 30, 30, and 31 days. Instead of a leap day, a full 7-day 'Xtr' week is inserted at the end of the year in certain years.

The Xtr month is a 7-day leap week appended at the very end of certain HHPC years to keep the calendar synchronized with the solar year. In the converter, you can enter month 13 to represent the Xtr month. Not every year has an Xtr month — it appears roughly every 5 to 6 years, similar in purpose to a leap day in the Gregorian system.

Xtr years in the HHPC are determined so that the calendar stays aligned with the Earth's orbit. Examples include 2015, 2020, 2026, 2032, 2037, 2043, and similar intervals. This converter automatically detects whether a given year is an Xtr year and shows that information in the results.

Proponents argue the HHPC offers significant economic and logistical advantages: scheduling becomes trivial since every date is always the same weekday, fiscal quarters are perfectly equal in length (91 days each), and international coordination is simplified. The calendar's creators also propose adopting Universal Time (UTC) globally alongside the calendar reform.

The HHPC proposal pairs calendar reform with adopting Coordinated Universal Time (UTC) worldwide, eliminating time zones entirely. Everyone on Earth would use the same clock reading simultaneously. This converter shows the calendar date conversion; actual UTC time adoption would be a separate social and policy change.

Each of the four HHPC quarters contains exactly 91 days (13 weeks) spread across three months: the first two months of each quarter have 30 days and the third month has 31 days. Quarter 1 = January, February, March; Q2 = April, May, June; Q3 = July, August, September; Q4 = October, November, December. In an Xtr year, the additional 7-day week follows December.

As of now, the HHPC has not been officially adopted by any country or international body. It remains a well-publicized academic and economic proposal championed by Johns Hopkins University economist Steve Hanke and astrophysicist Richard Henry. The target year for universal adoption was proposed as 2017, though adoption has not occurred.