dates.ijs

This script defines date and time utilities and is included in the J standard library. Definitions are loaded into the z locale.

Definitions

calendar (verb)

Returns calendar for year, as a list of months

Syntax

[opt] calendar year [months]

right argument is one or more numbers: year, months If no months are given, it defaults to all months.

optional left argument is startday of week,

0=sunday (default)
1=monday

Example

   calendar 2014 3 4
┌─────────────────────┬─────────────────────┐
│         Mar         │         Apr         │
│ Su Mo Tu We Th Fr Sa│ Su Mo Tu We Th Fr Sa│
│                    1│        1  2  3  4  5│
│  2  3  4  5  6  7  8│  6  7  8  9 10 11 12│
│  9 10 11 12 13 14 15│ 13 14 15 16 17 18 19│
│ 16 17 18 19 20 21 22│ 20 21 22 23 24 25 26│
│ 23 24 25 26 27 28 29│ 27 28 29 30         │
│ 30 31               │                     │
└─────────────────────┴─────────────────────┘

getdate (verb)

Get date from character string. Useful for input forms with date entry fields.

Syntax

[opt] getdate string

date forms permitted:
   1986 5 23
   May 23 1986
   23 May 1986

optional x:
 0 = days first - default (23 5 1986)
 1 = months first (5 23 1986)

Other characters allowed: ,-/:

If not given, century defaults to current

Only first 3 characters of month are tested.

Example

   getdate '23/5/86'
2086 5 23
   getdate 'may 23, 1986'
1986 5 23
   getdate '1986-5-23'
1986 5 23

isotimestamp (verb)

Format time stamps as: 2000-05-23 16:06:39.268

y is one or more time stamps in 6!:0 format.

todate (verb)

Converts day numbers to dates, converse todayno

This conversion is exact and provides a means of performing exact date arithmetic.

y = day numbers
x = optional:
  0 - result in form (default)
  1 - result in form
  2 - result in form

Example

   todate 72460
1998 5 23

   todate 0 1 2 3 + todayno 1992 2 27
1992 2 27
1992 2 28
1992 2 29
1992 3  1

todayno (verb)

Converts dates to day numbers, converse todate

y = dates

x = optional:
  0 - dates in form (default)
  1 - dates in form
  2 - dates in form

0 = todayno 1800 1 1, or earlier

Example

   todayno 1998 5 23
72460

tsdiff (verb)

Return differences between pairs of dates.

Syntax

end tsdiff begin

 end, begin are vectors or matrices in form YYYY MM DD
 end dates should be later than begin dates

method is to subtract dates on a calendar basis to determine integral number of months plus the exact number of days remaining. This is converted to payment periods, where # days remaining are calculated as: (# days)%365

Example

   1994 10 1 tsdiff 1986 5 23
8.35799

tsrep (verb)

Timestamp representation as a single number.

Syntax

[opt] timerep times

 opt=0 convert timestamps to numbers (default)
     1 convert numbers to timestamps

timestamps are in 6!:0 format, or matrix of same.

Example

   tsrep 1800 1 1 0 0 0
0
   x: tsrep 1995 5 23 10 24 57.24
6165887097240

tstamp (verb)

Same as [timestamp])#timestamp)

valdate (verb)

Validate dates.

Syntax

valdate dates

dates is 3-element vector
      or 3-column matrix
      in form YYYY MM DD

returns 1 if valid

weekday (verb)

Returns weekday from date, 0=Sunday ... 6=Saturday. Arguments as for todayno

Example

   weekday 1997 5 23
5
   1 weekday 19970523
5

weeknumber (verb)

Gives the year and weeknumber of date.

A week belongs to a year iff 4 days of the week belong to that year. see http://www.phys.uu.nl/~vgent/calendar/isocalendar.htm

y = dates In the ISO 8601 calendar a week starts on monday.

Example

   weeknumber 2005 1 2
2004 53
   weeknumber 2005 1 3
2005 1

weeksinyear (verb)

Gives number of weeks in year

y = years

In the ISO 8601 calendar a week starts on monday.

Example

  weeksinyear 2000 +i.10
52 52 52 52 53 52 52 52 52 53