月曆日轉儒略日(c2j)
Table of contents
背景
- 有關儒略日轉月曆日的轉換，可詳見j2c說明。此處為其反轉程式。
date(os) and datetime(py)
- 不論是bash或者是python的datetime，都有
+%j格式，可以輸出成julian day。設若輸入月曆日值為$ymd(+%Y%m%d)
bash
- date指令：
yyyyjjj=$( date -d "$ymd" +%Y%j) - 一般linux的date指令似乎會自行辨識輸入的日期格式(不含小時)
- 至少可以自動辨識+%Y%m%d及+%Y-%m-%d等2種。
- 不必(也不能)指定輸入格式。
- 如需此二者以外格式之輸入、或含有小時之日期
- 使用+%c(locale datetime)格式，如Thu Mar 3 23:05:25 2005
- 參考任意格式時間的讀取。
macOS
- date指令：
yyyyjjj=$( date -j -f "%Y%m%d" $ymd +%Y%j) - 輸入時間格式可以用-f 來指定
python datetime指令
- strptime
- point(export) the character string to datetime object
ymd_dt=datetime.datetime.strptime(ymd,'%Y%m%d')
- strftime
- create formatted string from datetime
yj=ymd_dt.strftime('%Y%j')
fortran程式碼(cal2jul.f)
- 此副程式剪裁自UAM及CAMx程式系統，現已不再更新。如在fortran程式內需進行日期的轉換可參考使用。
C$ cat ~/bin/cal2jul.f
character A100*100
call getarg(1,A100)
read(A100,*)jjj
call juldate(jjj)
write(*,'(I7)')2000000+jjj
stop
end
subroutine caldate(idate)
c
c-----CAMx v4.01 030625
c
c CALDATE converts date from Julian (YYJJJ) format to calender
c (YYMMDD) format
c
c Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
c ENVIRON International Corporation
c
c Modifications:
c none
c
c Input arguments:
c idate julian date (YYJJJ)
c
c Output arguments:
c idate calender date (YYMMDD)
c
c Routines Called:
c none
c
c Called by:
c AREAPREP
c BNDPREP
c CNCPREP
c DRYDEP
c PIGPREP
c RDPTHDR
c READZP
c STARTUP
c
dimension nday(12)
data nday/31,28,31,30,31,30,31,31,30,31,30,31/
c
c-----Entry point
c
c-----If it is already in calender date, return
c
if (idate.gt.100000) goto 9999
iyear = idate/1000
jday = idate - iyear*1000
c
nday(2) = 28
if (mod(iyear,4).eq.0) nday(2) = 29
mday = 0
do 10 imonth = 1,12
mday = mday + nday(imonth)
if (mday.ge.jday) go to 20
10 continue
20 iday = jday - (mday - nday(imonth))
idate = iyear*10000 + imonth*100 + iday
c
9999 return
end
c-------------------------------------------------------------
subroutine juldate(idate)
dimension nday(12)
data nday/31,28,31,30,31,30,31,31,30,31,30,31/
c
c-----Entry point
c
iyear = idate/10000
imonth = (idate - iyear*10000)/100
iday = idate - iyear*10000 - imonth*100
nday(2) = 28
if (mod(iyear,4).eq.0) nday(2) = 29
IF(IDAY.GT.NDAY(IMONTH).OR.IDAY.LE.0) THEN
IDATE=-1
RETURN
ENDIF
c
mday = 0
do 10 n = 1,imonth-1
mday = mday + nday(n)
10 continue
jday = mday + iday
idate = iyear*1000 + jday
c
return
end