September 13
Let an agent handle September 13 as a calendar date with weekday computation, observances attributed to their traditions and sourced events.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent handle September 13 as a calendar date with weekday computation, observances attributed to their traditions and sourced events.
September 13, day 256 (day 257 in leap years) of the year in the Gregorian calendar, with 109 days remaining in both common and leap years. September 13 is the Day of the Programmer in common years, when it is the 256th day, and the anniversary of the Battle of the Plains of Abraham at Quebec in 1759, of the start of the bombardment of Fort McHenry in 1814, of the Attica prison uprising being ended by force in 1971 and of the signing of the first Oslo Accord in Washington in 1993.
What it is for: A calendar date for scheduling, holidays and anniversaries.
It can be compute its weekday in a given year; check local and international observances; find sourced historical events; schedule events.
Distinguishing features
The thirteenth day of September
Weekday varies by year
Observances vary by place
Julian and Gregorian dates differ by 13 days in this era
What it looks like
A date on calendars.
Physical character
day of year: 256 or 257 day - common year, leap year where different
days remaining: 109 days
How it is recognised
Written 13 September or September 13
ISO format --09-13
Observances vary by country and tradition
Related models
is part of - month
follows - date
is a kind of - category
is expressed in - notation
In practice
Families and kinds
the recurring calendar date
specific dated days in given years
Identifiers
ISO 8601 --09-13 recurring date
Standards and regulation
ISO 8601
National public holiday laws
Failure modes and hazards
Assuming observances are universal
Unsourced on-this-day events
Mixing Julian and Gregorian dates
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Date Calendar facts.
Calendar arithmetic.
Weekday
Computation.
Weekday
Weekday.
- On which weekday does September 13 fall in this year? measurement
- Is it a leap year? boundary
Calendar
Julian or Gregorian.
Calendar
Calendar system.
- Is the Julian or Gregorian calendar meant? boundary
- What is the equivalent date in the other calendar? measurement
Observances Holidays.
Observances vary.
Holiday
Public holiday.
Holiday
Holiday status.
- Is September 13 a public holiday or observance here? provenance
- Which tradition or law sets it? provenance
Attribution
Traditions.
Attribution
Attributed observances.
- Which countries or communities observe something on this date, according to them? provenance
- Is the observance attributed rather than assumed? boundary
History Past events.
Events need sources.
Events
On this day.
Events
Historical events.
- Which notable events happened on September 13, according to reliable sources? provenance
- Are dates given in the same calendar? boundary
Anniversaries
Recurring.
Anniversaries
Anniversaries.
- Which anniversaries fall on this date this year? provenance
- Which are round numbers? measurement
Planning Scheduling.
Dates drive plans.
Countdown
Days until.
Countdown
Countdown.
- How many days until the next September 13? measurement
- From which date? definition
Work
Working day.
Work
Working day.
- Is it a working day for this organisation? provenance
- Do deadlines move? boundary
What the second pass must settle
- Should dated days be separate entries?
- How should observances be linked?
- How should events be sourced?