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I write a lot, a lot of personal journals in a plain text. They contain a lot of dates and times, many of them should be ideally tracked automatically (like, if I've written "15:00 tomorrow" some software ought to alarm at that time), so they should be written in a consistent manner. So far I've used ISO 8601 date and time format (e.g. 2020-09-05 or 11:30) and a bunch of natural extensions (e.g. tomorrow, last Sun).
And folks, it's verbose or often ambiguous to other plain text! For example I tend to schedule things in a multiple of hours so :00 is not necessary, but a single number 15 would be less recognizable as hours. Many systems will helpfully try to recognize at 15 or 3pm, but how would you know that at 15 is not a part of at 15 km/h or similar? Also my journals are in Korean anyway, and such workarounds tend to not work well crosslingually. How about the intervals like 15:00 thru 18:30? ISO 8601 interval 15:00/18:30 would be particularly problematic because a solidus is used for a lot of other things (honestly it reads like "twice at 15:00 and at 18:30" to me) and the format offers no more compact alternatives.
I need something that is compact, very distinguishable and eventually readable once I've practiced quite a bit. It should have the same amount of information as I would like to write, and don't have to be readable at the first glance (I know no one would bother to learn it anyway).
The Notation
The timepoint is written [<date>] @ [<time>], where <date> is 1--4 alphanumeric letters and <time> is 1--2 alphanumeric letters. It can't be preceded or followed by other alphanumeric letters.
At least one of <date> or <time> should be present.
The timepoint is absolute if <date> contains the year information. Otherwise it is relative to a reference timepoint.
<date> is either [[<year>] <month>] <day-of-month> [<day-of-week>] or [<relative-week>] <day-of-week> or <relative-date>.
If <day-of-month> is present, <day-of-week> is redundant and only used to aid the reading. Compare with "Saturday, September 5, 2020".
<day-of-month> is distinct from <day-of-week> or <relative-date>.
<month> and <day-of-month> should have different cases if both are alphabets. <month> has two sets of alphabets for this reason.
<time> is <half-hour> [<minute>].
There is no <second>. I don't need one.
<half-hour> and <minute> should have different cases if both are alphabets. <minute> has two sets of alphabets for this reason.
The time interval is written <timepoint> - <timepoint>, where the second timepoint is interpreted with the first timepoint as a reference timepoint.
If the first timepoint ends with @ or the second timepoint starts with @, that @ can be omitted. Therefore <date> @ <time1> - <time2> would denote an interval within a single date.
If the second timepoint has no date part and is earlier than the first timepoint, the second timepoint is reinterpreted with the reference timepoint plus one day. This allows for more compact short interval including the midnight.
I also personally allow ? to follow the timepoint to signal the uncertainty, which gets ignored by the time interval syntax.
Alphanumerics
This notation makes use of the following 58 letters:
0 1 2 3 4 5 6 7 8 9
A B C D E F G H I J K M N P Q R S T U V W X Y Z
a b c d e f g h i j k m n p q r s t u v w x y z
This list omits L/l and O/o. It might be surprising that I/i is not omitted, and that's because 1/I tends to be much more distinguishable than 1/l or I/l. It might be possible to omit only l or O as well, but having both cases for the same alphabet helps mnemonics.
24 alphabets are used mainly in two ways:
Two groups of 12 (A-M then N-Z): Used for multiples of 12.
It is a lucky coincidence that the second group starts with N, i.e. "noon".
Groups of 10 (A-J), 10 (K-V) then 4 (W-Z): Used for pretty much everything else.
The last group of 4 is left over and assigned to specials when combined with decimal digits, as dividing by 34 would be unpleasant.
z and x frequently refer to "previous" and "next", respectively.
<year>
0
1
2
3
4
5
6
7
8
9
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
A
B
C
D
E
F
G
H
I
J
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
K
M
N
P
Q
R
S
T
U
V
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
Other letters are reserved. Lowercased letters are avoided, as typos in this position would create much havoc.
<month>
1
2
3
4
5
6
7
8
9
0
N/n
D/d
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
As noted earlier, November and December can vary by the following <day-of-week>. Again, case distinction is avoided for the same reason as <year>.
<day-of-month>
A
B
C
D
E
F
G
H
I
J
1
2
3
4
5
6
7
8
9
a
b
c
d
e
f
g
h
i
j
10
11
12
13
14
15
16
17
18
19
K
M
N
P
Q
R
S
T
U
V
20
21
22
23
24
25
26
27
28
29
k
m
n
p
q
r
s
t
u
v
30
31
Empty slots (A and n through v) are reserved.
<relative-week>
z
missing
x
Last week
This week
Next week
See the next section for the definition of "week".
<day-of-week>
1
2
3
4
5
6
7
8
9
Last Sat
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Next Sun
The week spans from Sunday to Saturday. This is both a personal choice (I don't want to start a week with a workday) and a regional choice (Korean calendars commonly start a week with Sunday). You would want to alter this part if you ever choose to adapt this notation.
1 and 9 are beyond "this week", and thus can't be used with <relative-week>. When combined with <day-of-month> however they are equivalent to 8 and 2 respectively, so one can say that K9F8@ (2020-09-05 Sat) is followed by K9G9@ (2020-09-06 Sun), which is same to K9F2@.
<relative-date>
Z
z
0
x
X
Day before yesterday
Yesterday
Today
Tomorrow
Day after tomorrow
0@<time> is essentially same to @<time>, but can still be used to say "today" with no time parts (as @ alone is invalid).
<half-hour>
A
B
C
D
E
F
G
H
I
J
K
M
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
11:00
a
b
c
d
e
f
g
h
i
j
k
m
0:30
1:30
2:30
3:30
4:30
5:30
6:30
7:30
8:30
9:30
10:30
11:30
N
P
Q
R
S
T
U
V
W
X
Y
Z
12:00
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
23:00
n
p
q
r
s
t
u
v
w
x
y
z
12:30
13:30
14:30
15:30
16:30
17:30
18:30
19:30
20:30
21:30
22:30
23:30
<minute>
0
1
2
3
4
5
6
7
8
9
:00
:01
:02
:03
:04
:05
:06
:07
:08
:09
:30
:31
:32
:33
:34
:35
:36
:37
:38
:39
a
b
c
d
e
f
g
h
i
j
:10
:11
:12
:13
:14
:15
:16
:17
:18
:19
k
m
n
p
q
r
s
t
u
v
:20
:21
:22
:23
:24
:25
:26
:27
:28
:29
A
B
C
D
E
F
G
H
I
J
:40
:41
:42
:43
:44
:45
:46
:47
:48
:49
K
M
N
P
Q
R
S
T
U
V
:50
:51
:52
:53
:54
:55
:56
:57
:58
:59
As noted earlier, <half-hour> has different cases for half-hours starting at :00 and :30 and minutes should have the different case.
Examples
Timepoint
Interpretation
K9F@Nr
September 5, 2020 at 12:25
K9F@
September 5, 2020
K9F8@
Saturday, September 5, 2020
K9F1@
(Last) Saturday, September 5, 2020
9F@
September 5 of this year
F@
5th day of this month
8@
This Saturday
9@
Next Sunday
x2@
Next Sunday
@N
12:00 today
@Nr
12:25 today
@n
12:30 today
@nR
12:55 today
Time interval
Interpretation
K9k-0C@
September 30, 2020 (K9k@) through October 2 (K0C@)
Z-x@
The day before yesterday (Z@) through tomorrow (x@)
z@y-0@B
22:30 yesterday (z@y) through 1:00 today (0@B)
z@y-B
22:30 yesterday (z@y) through 1:00 (@B, implicitly today)
z@N-n
12:00 yesterday (z@N) through 12:30 (@n, implicitly yesterday)
@N1-n
12:01 today (@N1) through 12:30 (@n)
Extensions
I don't really need more than what is currently specified, but for the completeness the following list of extensions is suggested. They might or might not be useful for certain purposes, thus are declared optional but do not contradict each other.
Seconds and Beyond
<minute> can be suffixed by the optional <second> [<subsecond>].
<second> is 00 through 59, or 60 for the leap second.
<subsecond> is one or more decimal digits.
Alphabets in this position are reserved for other purposes.
Extended timepoint
Interpretation
@N000
12:00:00
@n456789
12:34:56.789
GDm@zV60
December 31, 2016 at 23:59:60 (would be a leap second in UTC)
Year Numbers Beyond 2000--2029
<year> can be prefixed by the optional <half-century>.
<half-century> is a half-century number and determines which (proleptic) Gregorian year is written as 0 in the subsequent <year>.
The half-century is numbered with a half-integer: 20th is around 2000, 20.5th is around 2050, 0th is around 1 BCE, -3.5th is around 351 BCE.
The last letter of <half-century> is either A through J (0 through 9) or a through j (0.5 through 9.5).
The first (but not last) letter of <half-century> might be b when the half-century number is negative.
Other letters are decimal digits.
<half-century> should be at least one letter long and bA (would be -0th half-century) is not permitted.
If <half-century> is present, <year> can contain a through v to represent 20--1 years before the year 0.
If <half-century> is not present, lowercased letters can't be used and 0 through V still mean years 2000--2029. (In the other words, they are implicitly prefixed by 2A, i.e. the 20th half-century.)
The 0th half-century is always explicitly written for this reason.
Extended timepoint
Interpretation
2A01A@
January 1, 2000 (same to 01A@)
1jK1A@
January 1, 1970 (20 years after 1950, around 19.5th half-century)
1Gc0F@
October 15, 1582 (18 years before 1600, around 16th half-century)
A01A@
January 1, 1 BCE in the proleptic Gregorian calendar
AvDm@
December 31, 2 BCE in the proleptic Gregorian calendar
bBVDm@
December 31, 32 BCE in the proleptic Gregorian calendar
b4HhnQ3@N
Monday, November 24, 4714 BCE (13 years before 4701 BCE) in the proleptic Gregorian calendar at 12:00
Extended Related Dates
Both <relative-week> and <relative-date> can be additionally be <number> z or <number> x for " weeks/days ago/later".
<number> is one or more decimal digits, which doesn't start with 0.
z and x are short for 1z and 1x.
Z and X (for <relative-date>) are short for 2z and 2x.
Both <year> and <month> can additionally be <relative-year> or <relative-month>, respectively.
Both <relative-year> and <relative-month> are [<number>] z or [<number>] x with the usual meaning.
<relative-year> and <relative-month> can't be used together.
When <relative-month> is in use, <day-of-month> can be p through v, indicating the 7th- to 1st-last day of that month.
Extended timepoint
Interpretation
3z5@
the third-to-last Wednesday
10x7@
the tenth-next Friday
xA@
the first day of the next month
3zu@
the second-to-last day of the third-to-last month
60zdR@
December 25, 60 years ago
Referencing Years, Months and Weeks
The timepoint can additionally be <year> Y, [<year>] <month> X, <relative-week> W or WW.
<month> in this context would be always lowercased (because X is uppercased).
WW refers to the current week.
X@ still refers to the day after tommorow; it requires an additional letter to become a month reference.
Extensions to <year>, <month> and/or <relative-week> equally apply.
Extended timepoint
Interpretation
WW@
this week
zW@
last week
xW@
next week
DX@
December this year
K0X@
October 2020
KY@
year 2020
If extended relative dates are in use, <relative-year> Y, YY, <relative-year> <month> X, <relative-month> X and XX are also allowed.
YY refers to the current year.
XX refers to the current month.
Extended timepoint
Interpretation
XX@
this month
zX@
last month
xX@
next month
3xX@
third-next month
x1X@
January of the next year
YY@
this year
xY@
next year
1000xY@
1000 years later
Time Zones
<time> can be followed by the optional Z [<tzoff-hour> [<tzoff-minute>]] or x <tzid>.
Z alone indicates UTC.
<tzoff-hour> is either A through Z (+00:00 through +23:00) or a through z (-00:00 through -23:00).
<tzoff-minute> is either 00 through 59, w/W (:15), x/X (:30) or y/Y (:45).
The minutes are always added to the offset's absolute value. ZA30 is +00:30, Za30 is -00:30.
If <tzoff-minute> is a single alphabet, its case should differ from <tzoff-hour>.
The empty <time> can't be followed by the time zone. It should at least have <half-hour>.
The timepoint without Z or x inherits the time zone from the reference timepoint.
The default reference timepoint has the unspecified local time zone.
Extended timepoint
Interpretation
@mZ
11:30 UTC
@mZJ
11:30 UTC+9:00
@mFZJw
11:45 UTC+9:15
@mFZiX
11:45 UTC-8:30
@mF10ZN45
11:45:10 UTC+12:45
z@mF10xKRSEL
yesterday at 11:45:10 in Korea Standard Time (Asia/Seoul)
See also
Hundred Rabbits have the Arvelie date format, retaining only the Gregorian year number and ticking around 2 week units. Believe it or not, Its motivation is as practical as this notation is.
