NB.* datetime.ijs: date and time fns.
NB. load '~addons/sfl/sfldates.ijs' NB. Use C++ Std Template Lib for dates
require 'dates format'
NB.* moAbbrevs: 3-letter (English) month abbreviations
NB.* baseDPM: base # of days per month (Feb->28)
NB.* weekDayAbbrevs: 3-letter (English) weekday abbreviations
NB.* cvtTS21Num: convert J (or APL) timestamp to YYYYMMDD.(day fraction).
NB.* cvtTmAPMil: convert [h]h:mm[ap] timestamp to hh:mm:00 format.
NB.* calendar: return text calendar for Year-Month YM (in form YYYYMM).
NB.* fmtHMS: format hours, minutes, seconds as string given 3 numbers.
NB.* elapsedTimeMsg: show time elapsed given starting qai=: 6!:1 ''.
NB.* isLaterThan: given timestamp is (1) later than now or not (0).
NB.* DateTimeCvt: Convert between DOS-style time (YYYYMMDD hh:mm[a|p]) & dayfraction.
NB.* DOSTime2DayFrac: DOS date & time MM/DD/YYYY hh:mm[a|p] -> YYYYMMDD.day-fraction.
NB.* monthAdd: add y months to x date YYYYMMDD.
NB.* DateAdd: limited mimic of VB DateAdd - DateAdd <unit to add>;date;num
NB.* waitUntil: wait until time y in [abbreviated] TS form: YYYY MM DD [[hh] [[mm] [[ss]]]]
NB.* adt2sqldt: MS Access date time 'M/D/Y h:m:s'->#M/D/Y#
NB.* yy2yyyy: 2-digit to 4-digit year; <:50 is pivot.
NB.* cvtIfDate2Num: assuming slash means [m]m/[d]d/[yy]yy date, convert to YYYYMMDD.
NB.* calcEOMdates: calculate End-Of-Month dates starting in year 0{y for
NB.* cvtAT: convert vector of timestamps from MSAccess DB to numeric date YYYYMMDD.
NB.* JDCNV: Julian day conversion from http://www.astro.washington.edu/deutsch-bin/getpro/library01.html?JDCNV
NB.* TSDiff: timestamp difference - return difference between 2 timestamps
NB.* TSAdd: add 2 timestamps - return sum of 2 timestamps
NB.* cvtDateTime2numDt: convert multiple (e.g. MS Access) char date-times, e.g.
NB.* dow: Day-of-week for year month day: 0=Sunday
NB.* toJulian: convert YYYYMMDD date to Julian day number.
NB.* toGregorian: convert Julian day numbers to dates in form YYYYMMDD
NB.* cvtY4M2D22YMD: "2002-06-11" -> 20020611 (numeric)
NB.* cvtMDY2Y4M2D2: convert char [m]m/[d]d/[yy]yy -> yyyymmdd (numeric);
NB.* cvtY4M2D22MDY: convert yyyymmdd (numeric) -> [m]m/[d]d/yyyy (char)
NB.* addMos: add N months to date in form Y4M2 (YYYYMM): YYYYMM addMos N.
moAbbrevs=: 'Jan';'Feb';'Mar';'Apr';'May';'Jun';'Jul';'Aug';'Sep';'Oct';'Nov';'Dec'
baseDPM=: 31 28 31 30 31 30 31 31 30 31 30 31 NB. Base # of days per month.
weekDayAbbrevs=: 'Sun';'Mon';'Tue';'Wed';'Thu';'Fri';'Sat'
NB.* cvtTS21Num: convert J (or APL) timestamp to YYYYMMDD.(day fraction).
cvtTS21Num=: 13 : '(100#.3{.y)+(5000+*/24 60 60 1000)%~24 60 60 1000#.3}.7{.y'"1
NB. Add 5 seconds to day length in case of leap seconds.
NB.* cvtTmAPMil: convert [h]h:mm[ap] timestamp to hh:mm:00 format.
cvtTmAPMil=: 3 : 0
tm=. <;._1 ':',y-.'mM'
ap=. {:>_1{tm
tm=. (}:&.>_1{tm) _1}tm
hr=. ".>0{tm
hr=. hr+12*(ap e. 'pP')*.12~:hr
tm=. (<":hr) 0}tm
(;tm,&.>':'),'00'
)
NB.* calendar: return text calendar for Year-Month YM (in form YYYYMM).
calendar=: 3 : 0
if. 158210>:y do. 'Date must be after 158210 (October 1582).'
else.
mos=. 'Jan';'Feb';'Mar';'Apr';'May';'Jun';'Jul';'Aug';'Sep';'Oct';'Nov';'Dec'
days=. 'Sun';'Mon';'Tue';'Wed';'Thu';'Fri';'Sat'
fom=. dow 0 100 100#:>:100*y NB. Day-of-week of first day of month.
'yr mo'=. 0 100#:y
len=. 28+((~:/0=4 100 400 4000|yr)*2=mo)+(2~:mo)*2+-.mo e. 9 4 6 11
cal=. days,":&.>6 7$(-fom)|.42{.":&.>>:i.len
cal=. ,/"2 >(->:>./,#&>cal){.&.>cal NB. Pad columns to >:max width
tit=. (":yr),~' ',~>mos{~<:mo
cal=. cal,~({:$cal)({.|.~[:-[:<.[:-:[-[:#]) tit NB. Center title
end.
NB.EG calendar 200705 NB. Calendar for May 2007
)
NB.* fmtHMS: format hours, minutes, seconds as string given 3 numbers.
NB.fmtHMS=: 3 : '}.;,'':'',&.>,&.>((<''zw2'')fmt&.>2{.y),<''zw6.3'' fmt 2}.y=. _3{.y'
fmtHMS=: 3 : '}.;'':'',&.>;((<''r<0>2.0'')8!:0&.>2{.y),<''r<0>6.3''8!:0]2}.y=. _3{.y'
NB.* fmtYMD: format year, month, day as string given 3 numbers.
fmtYMD=: 3 : '}.;''/'',&.>>(<''4.0'' 8!:0 {.y),(<''r<0>2.0'') 8!:0&.>_2{.y'
NB.* elapsedTimeMsg: show time elapsed given starting qai=: 6!:1 ''.
elapsedTimeMsg=: 3 : 0
'' elapsedTimeMsg y
:
elapsed=. y-~6!:1 '' NB. Seconds elapsed in session.
dhms=. 0 24 60 60#:elapsed NB. Days, hours, minutes, seconds
msg=. x,(CRLF#~0~:#x),'Done at ',(showdate ''),';',CRLF
tmunits=. }:;'/',~&.>((*3{.dhms)#'Days';'Hrs';'Mins'),<'Secs'
msg=. msg,'elapsed ',tmunits,': ',":dhms#~1,~*3{.dhms
)
isLaterThan=: 3 : '0< >0{(6!:0 '''') TSDiff 7{.y'
NB.* isLaterThan: given timestamp is (1) later than now or not (0).
DateTimeCvt=: 3 : 0
NB.* DateTimeCvt: Convert between DOS-style time (YYYYMMDD hh:mm[a|p]) & dayfraction
NB. (single number=<Julian day number>.<day fraction>).
if. ' '={.0$,y do. NB. Character ,T (Bnumber
'dt tm'=. <;._1 ' ',dsp ,y NB. Separate date and time
dt=. (toJulian cvtMDY2Y4M2D2 dt)+DOSTime2DayFrac tm
else. dt=. (cvtY4M2D22MDY toGregorian <.y),' ',DOSTime2DayFrac 0|y
end.
dt
)
DOSTime2DayFrac=: 3 : 0
NB.* DOSTime2DayFrac: DOS time hh:mm[a|p] -> 0.day-fraction or vice-versa.
'DOS' DOSTime2DayFrac y
:
spd=. 5+*/24 60 60 NB. Seconds per day + 5 for any leap seconds.
targ=. toupper x NB. Target direction->'DOS' or 'DF' (day fraction)
if. -.isNum y do. targ=. 'DF' end.
if. targ-:'DOS' do.
df=. (12|0{df) 0}df=. }:0 60 60#:<.0.5+spd*1|y
df=. ((0{df)+12*0=0{df) 0}df NB. 5 leap-seconds
df=. (}:;(2 lead0s&.>df),&.>':'),(0.4999<:1|y){'ap' NB. means noon<0.5.
else. df=. ;n2j&.><;._1 ':',y#~y e. ' 0123456789:' NB. '3:25p'->3 25
df=. ((0{df)+12*(12~:0{df)*.'pP'e.~{:y) 0}df
df=. ((0{df)-12*(12= 0{df)*.'aA'e.~{:y) 0}df
df=. 0.999999<.(60*60#.df)%spd
end.
df
)
NB.* monthAdd: add y months to x date YYYYMMDD.
monthAdd=: 4 : 0
mobase=. 0 12 31
100#.todate todayno 0 1 0+mobase#:(31*y)+mobase#.0 _1 0+0 100 100#:x
NB.EG 19590524 monthAdd 6+12*50
)
DateAdd=: 3 : 0
NB.* DateAdd: limited mimic of VB DateAdd - DateAdd <unit to add>;date;num.
NB. Date in form YYYYMMDD.
ts=. i. 0 [ units=. 'YMDW' NB. Units are Year, Month, Day, Week.
'unit dt addnum'=. y
assert (unit=. {.toupper unit) e. units
dpu=. (372 31 1 7){~units i. unit NB. 372=12*31: provisional "year"
mobase=. 0 12 31
assert. dt>18000101 NB. todayno only goes back to this date
dt=. 0 100 100#:dt
select. unit
case. 'D';'W' do.
dt=. 100#.todate (dpu*addnum)+todayno dt
case. 'M';'Y' do.
fakedayno=. mobase#.0 _1 0+dt
dt=. 100#.todate todayno 0 1 0+mobase#:fakedayno+dpu*addnum
end.
assert. dt>18000101 NB. todayno only goes back to this date
NB. dtdifs=. 2-/\todayno&>(<0 100 100)#:&.> dtsa=. DateAdd&>(<'D';20050101),&.><&.>i:_10000
NB. 1 *./ . = dtdifs
NB. dtdifs=. 2-/\todayno&>(<0 100 100)#:&.> dtsa=. DateAdd&>(<'W';20050101),&.><&.>i:_10000
NB. 7 *./ . = dtdifs
)
DateAddOLD=: 3 : 0
NB.* DateAdd: limited mimic of VB DateAdd - DateAdd <unit to add>;date;num
ts=. i. 0 [ units=. 'YMDW' NB. Units are Year, Month, Day, Week.
'unit dt add'=. y
unit=. {.toupper unit
assert unit e. units
if. 'W'=unit do. add=. 7*add [ unit=. 'D' end.
summand=. 6{.add (units i. unit)}(#units)$0
ts=. 100#.3{.>1{summand TSAdd 6{.0 100 100#:dt
NB.EG DateAdd 'D';20040524;_45
)
waitUntil=: 3 : 0
NB.* waitUntil: wait until time y in [abbreviated] TS form: YYYY MM DD [[hh] [[mm] [[ss]]]]
6!:3 (0>.>0{y TSDiff 6!:0 '')
NB.EG 'Happy New Year!' [ waitUntil 2004 12 31 23 59 59
)
adt2sqldt=: (1&|.)@('##'&,)@((]i.&' '){.]) NB.* MS Access date time 'M/D/Y h:m:s'->#M/D/Y#
yy2yyyy=: 3 : 0
NB.* yy2yyyy: 2-digit to 4-digit year; <:50 is pivot.
if. -.isNum yy=. y do. yy=. _".yy end.
yy+(yy<:50){1900 2000
)
cvtIfDate2Num=: 3 : 0
NB.* cvtIfDate2Num: assuming slash (or dash) means [m]m/[d]d/[yy]yy date,
NB. -> character yyyymmdd.
if. +./'-/' e. y do.
dlim=. {.y-.'0123456789' NB. Assume delimiter is 1st non-numeral.
y=. ":dlim cvtMDY2Y4M2D2 y
end.
y NB. Return input if not date.
)
cvtTS2Access=: 3 : 0
NB. cvtQTS2Access: convert J timestamp to MS Access date:
NB. YYYY MM DD hh mm ss.ms -> MM/DD/YYYY hh:mm:ss
if. 0=#y do. dt=. qts ''
else. dt=. 6{.y end.
dt=. (1 2 0 3 4 5 ){dt NB. Reorder YMD->MDY
dt=. (roundNums 5{dt) 5}dt NB. Round to whole seconds.
dt=. <("1)2 3$dt NB. Separate date & time.
dt=. (>":&.>&.>dt),&.>("1 0)'/:' NB. M D Y ->"M/D/Y/" & h m s ->"h:m:s:"
dt=. (_3{.&.>(<'00'),&.>1{dt) 1}dt NB. Pad time w/leading 0s.
dt=. }:&.>dsp&.><"1 ;"1 dt NB. Drop excess trailing delimiters,
dt=. }:;dt,&.>' ' NB. join date & time -> "M/D/Y hh:mm:ss"
NB.EG cvtTS2Access 6!:0 ''
)
normAccessDate=: 3 : 0
NB. normAccessDate: convert MS Access dates with usually useless timestamp
NB. to simple date, e.g. YYYY-MM-DD hh:mm:ss -> (numeric) YYYYMMDD.
if. isNum 0{y do. NB. YYYYMMDD -> 'MM/DD/YYYY'
xp=. 1 1 1 1 0 1 1 0 1 1 0
tmp=. y
dts=. ''
while. 0<#tmp do.
dd=. }.4|.xp exp ": >0{tmp NB. 20030524 -> 05 24 2003
dts=. dts,<'/' (b2i -.}.4|.xp)}dd NB. -> 05/24/2003
tmp=. }.tmp
end.
else. NB. YYYY-MM-DD hh:mm:ss -> YYYYMMDD
dts=. boxopen y
dts=. ;0".&.>'-'-.~&.>dts {.~ &.> dts i. &.> ' '
end.
dts
)
cvtAccessIODates=: 3 : 0
NB. cvtAccessIODates: stupid MS Access exports dates in form YYYY-MM-DD that
NB. it won't accept for import: convert between this and MM/DD/YYYY form.
y=. y{.~y i. ' ' NB. 2002-01-23 12:34:46 -> 2002-01-23
if. '-' e. y do. NB. Dash delimiter: YYYY-MM-DD -> MM/DD/YYYY
y=. (y='-')}y,:'/'
dt=. y
wh=. >:dt i. '/' NB. Pull off [YY]YY/
dt=. (wh}.dt),_1|.wh{.dt NB. YYYY/MM/DD -> MM/DD/YYYY
y=. dt,y}.~y i. ' ' NB. Put date back on first.
elseif. '/' e. y do. NB. Slash delimiter: MM/DD/YYYY -> YYYY-MM-DD
y=. (y='/')}y,:'-'
if. ' ' e. y do.
dt=. y
wh=. ->:(|.dt) i. '-' NB. Pull off "-[YY]YY"
dt=. (wh}.dt),~1|.wh{.dt NB. MM-DD-YYYY -> YYYY-MM-DD
y=. dt,y}.~y i. ' ' NB. Put date back on first.
end.
end.
y
)
calcEOMdates=: 3 : 0
NB.* calcEOMdates: calculate End-Of-Month dates starting in year 0{y for
NB. 1{y years. Account for weekends but not any holidays.
'styr numyrs'=. y
eomdts=. (styr+i.numyrs),&.>/(i.12) NB. Start with YYYY MM
eomdts=. eomdts,&.>(1{&.>eomdts) d14&.>0{&.>eomdts NB. ,last calendar day
eomdts=. eomdts+&.><0 1 0 NB. Origin-1 months
dd=. dow&.>eomdts NB. Days-of-week
weekdayshift=. dd{&.><2 0 0 0 0 0 1 NB. Move back 2 days for Sunday,
eomdts=. eomdts-&.>(<0 0),&.>weekdayshift NB. or 1 for Saturday
NB. Returns (numyrs,12)$<YYYY MM DD date numbers.
NB.EG eomdts=. calcEOMdates 2003 5
)
cvtAT=: 3 : 0
NB.* cvtAT: convert vector of timestamps between MS Access DB form
NB. 'MM/DD/YYYY hh:mm:ss' and numeric date YYYYMMDD.
if. isNum y do.
cvtTS2Access 0 100 100#:y
else. cvtDateTime2numDt y end.
)
JDCNV=: 3 : 0
NB.* JDCNV: Julian day conversion from http://www.astro.washington.edu/deutsch-bin/getpro/library01.html?JDCNV
'yr mn day hr'=. y
NB. yr = long(yr) & mn = long(mn) & day = long(day);Make sure integral
L=. (mn-14)%12 NB. In leap years, -1 for Jan, Feb, else 0
julian=. day-32075+(1461*(yr+4800+L)%4)+(367*(mn - 2-L*12)%12) - 3*((yr+4900+L)%100)%4
julian=. julian+(hr%24)-0.5
)
TSDiff=: 4 : 0
NB. Still has bug: will give year, month, or day of 0.
NB.* TSDiff: timestamp difference - return difference between 2 timestamps
NB. in form Y M D h m s= years months days hours minutes seconds.
timebase=. 0 12 31 24 60 60
'x y'=. (#timebase){.&.>x;<y NB. Pad trailing with 0s if missing.
secs=. ;(<timebase)#.&.>x;<y
swaphilo=. 0
if. </secs do. swaphilo=. 1 [ secs=. |.secs end.
diff=. timebase#: ds=. -/secs
if. swaphilo do.'ds diff'=. -&.>ds;diff end.
ds;diff NB. Difference in both seconds and in Y M D h m s.
NB.EG (6!:0 '') TSDiff ts [ 6!:3,10 [ ts=. 6!:0 '' NB. 10-sec delay
)
TSAdd=: 4 : 0
NB. Still has bug: will give year, month, or day of 0.
NB.* TSAdd: add 2 timestamps - return sum of 2 timestamps
NB. in form Y M D h m s= years months days hours minutes seconds.
timebase=. 0 12 31 24 60 60
'x y'=. (-#timebase){.&.>x;<y NB. Pad leading with 0s if missing.
secs=. ;(<timebase)#.&.>x;<y
sum=. timebase#: ds=. +/secs
ds;sum NB. Difference in both seconds and in Y M D h m s.
NB.EG (6!:0 '') TSAdd 10 15 NB. 10 min, 15 seconds from now.
)
showdate=: 3 : 0
NB. showdate: show given, or current if arg '', date & time in standard form.
NB. Can show 60 in seconds position because rounded to nearest second and
NB. carrying because of rounding gets too complicated.
y=. ,y NB. Must be vector.
if. 0=#y do. y=. 6!:0 '' end. NB. Arg is timestamp: YYYY MM DD hh mm ss
dt=. fmtYMD 3{.y
if. 3=#y do. tm=. '' else.
tm=. fmtHMS 3}.y
if. 0=1|_1{y do. tm=. tm{.~tm i: '.' end. NB. Drop fraction of second if none
end.
dt,(' '#~0~:#tm),tm
NB.EG showdate 1959 5 24 8 9 0
NB.EG showdate '' NB. Current date and time
NB.EG >}.<;._1 ' ',showdate '' NB. Time only
NB.EG showdate 1992 12 16 NB. Date only
)
cvtDateTime2numDt=: 3 : 0
NB.* cvtDateTime2numDt: convert multiple (e.g. MS Access) char date-times, e.g.
NB. "1995-02-28 00:00:00", to numeric dates, e.g. 19950228.
dt=. boxopen y=. ,y
dlim=. ('-' e. >0{dt){'/-'
dt=. dt {.~ &.> ' 'i.~ &.> dt
dt=. ;dlim cvtY4M2D22YMD dt
NB.EG cvtDateTime2numDt '1995-05-31 12:34:56';<'1995-06-30 00:00:00'
)
cvtD2M3Y22MSDSY=: 3 : 0
NB. cvtD2M3Y22MSDSY: e.g. 31-Jul-02 -> 7/31/02.
if. 0~:#y do.
y=. ,y
dlim=. {.~.y -. '0123456789' NB. Assume delimiter whatever not num.
dt=. <;._1 dlim,y
mo=. >:(toupper &.> moAbbrevs) i. <toupper >1{dt
}:;(":&.>mo;0 2{dt),&.>'/'
else. y end.
)
m11=: 0: ~:/ .= 4 100 400"_ |/ ] NB. Is y a leap year?
m12=: 28"_ + m11@] NB. Number of days in February of year y
d13=: 31"_ - 2: | 7: | [ NB. days in month x, not = 1
d14=: d13`m12@.([=1:) NB. Number of days in month x of year y
m22=: -/@:<.@(%&4 100 400)"0 NB. # of leap days in year yyyy (Clavian corr.)
m21=: >:@(365&* + m22)@(-&1601) NB. # of New Year's Day, Gregorian year y; m21 1601 is 1.
dowsoy=: 7&|@m21 NB. Day of week for start of year YYYY: 0=Sunday
dow=: 3 : 0
NB.* dow: Day-of-week for year month day: 0=Sunday
7|+/(dowsoy 0{y),(;(i. 0>. <:1{y) d14 &.> 0{y),<:2{y
)
isLeapYr=: 0: ~:/ .= 4 100 400"_ |/ ]
toJulian=: 3 : 0
NB.* toJulian: convert YYYYMMDD date to Julian day number.
dd=. |: 0 100 100 #: y
mm=. (12*xx=. mm<:2)+mm=. 1{dd
yy=. (0{dd)-xx
nc=. <.0.01*yy
jd=. (<.365.25*yy)+(<.30.6001*1+mm)+(2{dd)+1720995+2-nc-<. 0.25*nc
NB.EG toJulian 19590524 19921216
)
toGregorian=: 3 : 0
NB.* toGregorian: convert Julian day numbers to dates in form YYYYMMDD
NB. (>15 Oct 1582). Adapted from "Numerical Recipes in C" by Press,
NB. Teukolsky, et al.
igreg=. 2299161 NB. Gregorian calendar conversion day (1582/10/15).
xx=. igreg<:ja=. <. ,y
jalpha=. <.((<.(xx#ja)-1867216)-0.25)%36524.25
ja=. ((-.xx) expand (-.xx)#ja)+xx expand (xx#ja)+1+jalpha-<.0.25*jalpha
jb=. ja+1524
jc=. <.6680+((jb-2439870)-122.1)%365.25
jd=. <.(365*jc)+0.25*jc
je=. <.(jb-jd)%30.6001
id=. <.(jb-jd)-<.30.6001*je
mm=. mm-12*12<mm=. <.je-1
iyyy=. iyyy-0>iyyy=. (<.jc-4715)-mm>2
gd=. (10000*iyyy)+(100*mm)+id
)
NB. Date fns: convert between different date formats.
cvtY4M2Mos=: 3 : '12#.(0 100#:y)-0 1' NB. 200011 -> 24011
cvtMo2Y4M2=: 3 : '100#.0 1+0 12#:y' NB. 24010 -> 200010
cvtMDY2Y4M2=: (".)@((_4&{.),(2&{.)) NB. "11/30/1999" -> 199911 (numeric)
cvtY4M2D22YMD=: 3 : 0
NB.* cvtY4M2D22YMD: "2002-06-11" -> 20020611 (numeric)
'-' cvtY4M2D22YMD y
:
if. 0~:#y do.
dlim=. x
dts=. (dts i. &.>' '){.&.>dts=. boxopen y
dts=. ((5}.&.>dts),&.>dlim),&.>4{.&.>dts
dts=. dlim cvtMDY2Y4M2D2 &.> dts
else. y end.
NB.EG dts=. cvtY4M2D22YMD '1959-5-24';'1992-12-16';<'1959-05-06'
)
cvtMDY2Y4M2D2=: 3 : 0
NB.* cvtMDY2Y4M2D2: convert char [m]m/[d]d/[yy]yy -> yyyymmdd (numeric);
NB. x is optional delimiter character if not '/'.
'/' cvtMDY2Y4M2D2 y NB. Assume slash delimiter.
:
if. 0~:#y do.
ptn=. <;._1 ((x~:0{y)#x),y
assert. *./isValNum&>ptn NB. All date parts should be numeric.
ymd=. ".&.>ptn
if. 100 > year=. >2{ymd do.
if. 80 > year do. year=. year+2000
else. year=. year+1900 end.
ymd=. (<year) 2}ymd
end.
100#.;_1|.ymd
else. y end.
NB. cvtMDY2Y4M2D2&.>'3/14/01';'5/9/99';'2/6/1999';'12/16/79';'2/18/80'
NB. +--------+--------+--------+--------+--------+
NB. |20010314|19990509|19990206|20791216|19800218|
NB. +--------+--------+--------+--------+--------+
)
cvtY4M2D22MDY=: 3 : 0
NB.* cvtY4M2D22MDY: convert yyyymmdd (numeric) -> mm/dd/yyyy (char)
NB. x is optional delimiter character if not '/'.
'/' cvtY4M2D22MDY y NB. Assume slash is delimiter.
:
if. 0~:#y do.
y=. ''$y
dlim=. x
dt=. (":&.>1|.0 100 100#:y),&.>1 1 0{.&.>dlim
;_3 _3 _4{.&.>(<'0000'),&.>dt NB. Pad with leading 0s
else. y end.
NB.EG cvtY4M2D22MDY 19730131
)
cvtDDMMMYYYY2Y4M2D2=: 3 : 0
NB.* cvtDDMMMYYYY2Y4M2D2: convert, e.g 31-Mar-1995->19950331; use global moAbbrevs.
'dd mo yy'=. <;._1 '-',y
100#.(".yy),(>:moAbbrevs i. <mo),".dd
)
addMos=: 3 : 0
NB.* addMos: add N months to date in form Y4M2 (YYYYMM): YYYYMM addMos N.
(100 #. 2{.6!:0 '') addMos y NB. Assume current date if none given.
:
1+100#.0 12#:y+12#.0 100#:x-1
NB.EG 199909 addMos 16
NB.EG 200101
)
NB. From: "RISKS List Owner" <risko@csl.sri.com>
NB. Date: Sat, 27 Jul 2002 12:41:31 PDT
NB. Subject: [risks] Risks Digest 22.18
NB. To: risks@csl.sri.com
NB. .+--------------------+.
NB. Date: Wed, 24 Jul 2002 18:37:22 +0100
NB. From: John Stockton <spam@merlyn.demon.co.uk>
NB. Subject: Possible day-of-week error - Zeller
NB.
NB. Algorithms for determining the day-of-week from year-month-day -
NB. whether or not truly Zeller's - can, for certain dates, compute a negative
NB. number mod 7, which does not yield the desired result. Zeller himself
NB. dealt with this.
NB.
NB. Tests using "current" dates in the later 1900's would not have seen
NB. this problem.
NB.
NB. A good test date is 2001-03-01 (1st March 2001); the algorithm can
NB. easily be run manually.
NB.
NB. The problem has been seen, for example, in C code in an Internet draft.
NB.
NB. Those whose systems do suitable run-time checking may already have
NB. discovered the problem.
NB.
NB. John Stockton, Surrey, UK. http://www.merlyn.demon.co.uk/programs/
NB. Dates: miscdate.htm moredate.htm js-dates.htm pas-time.htm critdate.htm
NB. etc. 