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The Hanke-Henry Permanent Calendar, devised by Steve H. Hanke and Richard Conn Henry, is a proposed new calendar which aims to reform the current Gregorian Calendar by making every year identical. With the Hanke-Henry Permanent Calendar, every calendar date always falls on the same day of the week. It used to be basically the same as the Common-Civil-Calendar-and-Time calendar, but has been changed to start the week on Monday.
Today is 2024-04-11 in the (revised) HHPC compared to 2024-04-11 according to the ISO 8601 implementation of the Georgian calendar.
In 2004, Richard Conn Henry, a professor of astronomy at Johns Hopkins University, proposed the adoption of a calendar known as Common-Civil-Calendar-and-Time, which he described as a modification to a proposal by Robert McClenon. This version had essentially the same structure given above, but inserted its leap week named "Newton" between June and July. The leap rule was chosen to match the ISO week leap rule, to minimize the variation in the start of the year relative to the Gregorian calendar.
He had advocated transition to the calendar on January 1, 2006 as that is a year in which his calendar and the Gregorian calendar begin the year on the same day. After that date passed, he recommended dropping off December 31, 2006 to start in 2007, or dropping December 30 and 31, 2007 to start 2008.[1]
In late 2011 the calendar was revised by Johns Hopkins economist Steve Hanke by moving the leap week from the middle to the end of the year and renaming it "Extra", producing the Hanke-Henry Permanent Calendar. The target date for universal adoption was January 1, 2017 then, but has been postponed to 2018,[2] when the calendar design was changed in early 2016 to adopt Monday as the start of the week, quarter and year, to better comply with existing international standard ISO 8601.
Year layout[]
January
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W1
01
02
03
04
05
06
07
W2
08
09
10
11
12
13
14
W3
15
16
17
18
19
20
21
W4
22
23
24
25
26
27
28
W5
29
30
February
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W5
01
02
03
04
05
W6
06
07
08
09
10
11
12
W7
13
14
15
16
17
18
19
W8
20
21
22
23
24
25
26
W9
27
28
29
30
31
32
March
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W9
01
02
03
W10
04
05
06
07
08
09
10
W11
11
12
13
14
15
16
17
W12
18
19
20
21
22
23
24
W13
25
26
27
28
29
30
31
W15
32
33
34
35
April
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W14
01
02
03
04
05
06
07
W15
08
09
10
11
12
13
14
W16
15
16
17
18
19
20
21
W17
22
23
24
25
26
27
28
W18
29
30
May
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W18
01
02
03
04
05
W19
06
07
08
09
10
11
12
W20
13
14
15
16
17
18
19
W21
20
21
22
23
24
25
26
W22
27
28
29
30
31
32
June
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W22
01
02
03
W23
04
05
06
07
08
09
10
W24
11
12
13
14
15
16
17
W25
18
19
20
21
22
23
24
W26
25
26
27
28
29
30
31
W28
32
33
34
35
July
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W27
01
02
03
04
05
06
07
W28
08
09
10
11
12
13
14
W29
15
16
17
18
19
20
21
W30
22
23
24
25
26
27
28
W31
29
30
August
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W31
01
02
03
04
05
W32
06
07
08
09
10
11
12
W33
13
14
15
16
17
18
19
W34
20
21
22
23
24
25
26
W35
27
28
29
30
31
32
September
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W35
01
02
03
W36
04
05
06
07
08
09
10
W37
11
12
13
14
15
16
17
W38
18
19
20
21
22
23
24
W39
25
26
27
28
29
30
31
W41
32
33
34
35
October
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W40
01
02
03
04
05
06
07
W41
08
09
10
11
12
13
14
W42
15
16
17
18
19
20
21
W43
22
23
24
25
26
27
28
W44
29
30
November
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W44
01
02
03
04
05
W45
06
07
08
09
10
11
12
W46
13
14
15
16
17
18
19
W47
20
21
22
23
24
25
26
W48
27
28
29
30
31
32
December
Week
1
2
3
4
5
6
7
Mon
Tue
Wed
Thu
Fri
Sat
Sun
W48
01
02
03
W49
04
05
06
07
08
09
10
W50
11
12
13
14
15
16
17
W51
18
19
20
21
22
23
24
W52
25
26
27
28
29
30
31
Xtra
01
02
03
04
05
06
07
The only difference from the International 30:30:31 Leap-Week Calendar is that HHPC puts the 53rd week in an extra mini-month instead of attaching it to the last month as December 32 through 38.
Correcting for drift[]
While many calendar reforms aim to make the calendar more accurate, the Hanke-Henry Permanent Calendar focuses on making the calendar perennial, so that every date falls on the same day of the week, year after year.[3] The familiar drift of weekdays with respect to dates results from the fact that the number of days in a physical year (one full orbit of earth around the sun, approximately 365.24 days) is not a multiple of seven. By reducing common years to 364 days (52 weeks), and adding an extra week every five or six years, the Hanke-Henry Permanent Calendar eliminates weekday drift and synchronizes the calendar year with the seasonal change as the Earth circles the Sun. The extra week, or "mini-month", known as "Xtr (or Extra)",[3] would occur every year that either begins or ends in a Thursday on the corresponding Gregorian calendar.[3] The extra week would fall between the end of December and the beginning of January. Leap weeks in 2015, 2020, 2026, 2032, 2037, 2043, 2048, 2054, 2060 …
Under the Hanke-Henry Permanent Calendar there are two 30 day months followed by one month of 31 days. While the Hanke-Henry Permanent Calendar changes the length of the months, the week and days remain the same.[4]
Advantages[]
Holidays such as Christmas and New Year's Day as well as birthdays always occur on the same day of the week every year.
The calendar itself is permanent, it does not change year to year, with the exception of the need to add a week at the end of every 5 or 6 years.
Quarters all have the same number of days simplifying financial calculations. This calendar would also have prevented Apple’s Q4 2012 reporting fiasco. [5]
Unlike many other reform proposals, it does not change the days of the week.
The calendar starts on the same day every year, Monday, 1 January.
As in the Gregorian calendar, Sunday to Sunday is always seven days, as is Saturday to Saturday, or Friday to Friday. Because no days are ever added outside a seven-day week, there should be no objection from religious groups concerned about weekly holy days. (In proposals that add single days outside the week, a true "seventh day" of rest or worship would drift between weekends and weekdays.)
Every year has 361 days whose dates also occur in the Gregorian calendar and every one of those dates occurs within 5 days of its Gregorian counterpart, unlike the Symmetry454 Calendar, which has fewer days whose dates also occur in the Gregorian calendar some of which occur 7 or more days from their Gregorian counterpart and others such as ISO week date the Week & Month Calendar, which have no date the same as a Gregorian date.
Disadvantages[]
Not as precisely aligned with the solar year as the existing Gregorian calendar and some proposed reform calendars.
Requires continued use of the Gregorian calendar for certain agricultural purposes.
All computer date-handling will have to be fixed, which will be much more complicated than the Y2K fix.
There is no 31st of October, removing Halloween from the current date (What about making Halloween October 30th?)
About 2 in 45 quarters are a whole week longer than the rest.
Most dates are the same as in the Gregorian calendar and so could cause confusion if used alongside the Gregorian calendar, unlike ISO week date and Week & Month Calendar.
