$! Convertion date from DCL format to julien format
$! Author: Antonio Vigliotti  antoniov@shs-av.it
$!
$! Julien date is the number of days since 1-1-0
$! Converted from a C routine
$! Original routine calculate change of calendar by pope Gregor XIII in 
$! year 1582. Therefor this DCL routine works only since 1582 (in Italy)
$! or since 1824 (in Greek). For other countries read history!
$! Julien date can be use to compare two dates.
$mloop:
$ inquire begdat "Beg.Date [dd-mmm-yyyy]"
$ if begdat.eqs."" then exit
$ inquire enddat "End Date [dd-mmm-yyyy]"
$ if enddat.eqs."" then exit
$ if enddat.lts.begdat then goto mloop
$ dt=begdat
$ gosub c2julien
$ begj=j
$ dt=enddat
$ gosub c2julien
$ endj=j
$ write sys$output enddat," - ",begdat," = ",endj-begj
$ goto mloop
$c2julien:
$ y=f$cvtime(dt,,"year")
$ m=f$cvtime(dt,,"month")
$ d=f$cvtime(dt,,"day")
$ j=y*365+(y+3)/4
$c2loop:
$ m=m-1
$ if m.eq.0 then goto c2xit
$ j=j+f$int(f$elem(m," ","0 31 28 31 30 31 30 31 31 30 31 30 31"))
$ goto c2loop
$c2xit:
$ j=j+d
$ return