datenumber.ijs

Script: ~addons/finance/finexec/datetime/datenumber.ijs
Contributor: William Szuch
Updated: 2022 5 26
Depend: nil
Definitions: loaded to locale base
Status: done
Script source: datenember.ijs

This is an exercise in building long tacits for todayno and todate.
Taken from the explicit definition in dates.ijs in stdlib
This script defines definitions that convert a date to a number
and a number to a date.
The J calendar starts from 1800 1 1 (Wed): day number = 0 eg: todate 0 gives 1800 1 1
also, 1 todate 0 gives 18000101
Use is made of the J addon: dates.ijs that is loaded to the z locale as
part of the stdlib.ijs.

Monday is the first day of the week as per: ISO 8601.
Index: Monday = 0, Sunday = 6 (Days = 0 1 2 3 4 5 6)
calendar 2009
1 calendar 2009 (ISO 8601)

In the ISO 8601 calendar is a week that starts on Monday.
1 YEAR = 365.2425 DAYS

Date format as a number: yyyy mm dd or yyyymmdd

The preferred date formats:
yyyymmdd eg: 19970630
yyyy mm dd eg: 1997 6 30

Use ‘getdate’ for conversion of character dates to format: yyyy mm dd.

An Excel date is a number displayed with a date format.
It starts from 1900 1 1 with a well known leap year bug.

To convert from J day numbers (result of verb ‘todayno’ in dates.ijs),to
Excel day number subtract 36522 from the J day number.

Definitions to be completed.
numbertodate/numbertodatex

Definitions

D	datenumbertable, datetonumber, datetonumberx
N	numbertodate, numbertodatex

datenumbertable (monad)

Form: explicit
depend: todate (stdlib: dates.ijs)
Table with 5 columns: yyyy mm dd daynumber yyyymmdd
1800 1 1 = 0 daynumber

Syntax

  datenumbertable(N,N1)
N = start day number
N1 = number of days

Example

  datenumbertable(0,2)
1800 1 1 0 18000101
1800 1 2 1 18000102

   datenumbertable(80353,4)
2020 1 1 80353 20200101
2020 1 2 80354 20200102
2020 1 3 80355 20200103
2020 1 4 80356 20200104

datetonumber (monad)

Form: tacit
Depend: nil
Based on explixit todayno from dates.ijs (stdlib)
Convert a date to a day number.

Syntax

datetonumber(D)
D = table of dates with format YYYY MM DD

Example

  datetonumber 2014 12 1
78496

  datetonumber (1998 3 23,:2014 12 1)
72399 78496

  datetonumber(1998 3 23,2014 12 1,2019 1 1,:2019 5 20)
72399 78496 79988 80127

datetonumberx (monad)

Form: tacit
Depend: nil
convert a date to a day number
Based on explicit todayno from dates.ijs (stdlib)

numbertodate (monad)

Form: tacit
Depend: nil
Convert a day number to a date
Based on explicit todate from dates.ijs (stdlib)

TO Do

Syntax

 numbertodate(D)
D = day number

numbertodatex (monad)

Form: tacit
Depend: nil
Convert a day number to a date
Based on explicit todate from dates.ijs (stdlib)

To Do

Syntax

   numbertodatex(D)
D = day number