RPN.2.d \ Julian arithmetic
[a]#'146097';
[b]#'1461';
[c]#'100';
[d]#'153';
[e]#'1721119';
[q]#'10000';

[f]
\Integer divide
r2g2/r2tH+w;

[g]
\Julian to MDY
ClCe-V
v4*1-CaCf Xc
v4*1-Caxc*-V
v4Cf Xb
xb4*3+CbCf V
xb4*3+vCb*-4+4CfXb
xb5*3-CdCfXa
xb5*3-xaCd*-5+5CfXb
xcCc*v+ Xc
xa#'10'<(xa3+Xa :
xa9-Xaxc1+Xc )
xaxbxc ;

[h]
\ MDY to Julian
Cm XcXbXa
xa2>(xa3-Xa :
xa9+Xaxc1-Xc)
xcCcCfV
xcCcv*-Xc
Cav*4CfCbxc*4Cf+Cdxa*2+5Cf+xb+Ce+ ;

[i]
\ MDY -> F
Cm XcXbXa
xd c(xcCq /xb+Cc/xa+ :
xcCc*xa+Cc*xb+ :
xcCq/ xa+ Cc/ xb+ :
xc xbCc/+ xaCq/+
) ;

[j]
\F -> MDY
g1 xd 
c(
  g1wXa fCc*g1wXbfCq*Xc :
  g1CqCfXc Cq%g1CcCfXaCc%Xb :
  g1wXbfCc*g1wXafCq*Xc :
  g1wXc fCc* g1wXb fCc*Xa
)
xcCmd1 xa 1 < xa #'12' > | xb 1 < | xb #'31'> | 
  (D'Invalid date format.|Ok|Change format|' 1=0 (Ct). )
d1
xaxbxc 
;

[k]
\Get Easter
g1 0< g2 #'9999'> | g2 g1 w =0 ! | (Cj d2 d2)
Cm  Xc xc #'19' % g1 c(4:4:3:4:3:4:4:3:4:4:3:4:4:3:4:3:4:4:3) Xa
c(#'14':3:#'23':#'11':#'31':#'18':8:#'28':#'16':5:#'25':#'13':2:#'22':#'10':#'30':#'17':7:#'27')

Xb 
xaxbxc ChV
{v1+Vv7%6=0(B:)}
v ;

[l]
\Validate Julian
g1 g1 Ce> r2 g1 #'5373485'<r3& g2 f0=0 &
(:D'Julian must be 1721120 to\  5373484|Ok|'d1.) d1;

[m]
\Validate year
g1 #'-1'> r2 g1 Cq<r3& g2 f0=0  &(:D'Year must be 0-9999|Ok|'d1.);

[n]
\Number of days per full moon
#'29.53058868';

[o]
\Offset of days for full moon
#'.6879';

[p]
\Phase of the moon
Cn / Co +;

[t]
\Select format
D'Use yyyy mm and dd for all\formats. E.g. 
m.dy=mm.ddyyyy|m.dy|ymd|d.my|y.md|cancel|'
g1 4=0(d1:Xd);

"Julian"

"set: Show the version and\select the date format" 
D'Julian Arithmetic version 1.05\By Jim Cook - March 22, 
2000|email|format|Ok|'
 c(D'jcook@halcyon.com|Ok|' d1:
 Ct :
 ) ;
"moon: Show the phase of the\moon\0=new .25=1Q .5=full .75=3Q"
?1 CjCh Cp f;

"full: Show the next full moon\Enter a date"
?1 CjCh Cp 1H +  w 1H + Co - Cn * 1H + w CgCi;

~
"now: Put today on the stack" {TD TMTDTY TD r5 =0(B)}  Ci;
"_>j: Convert date to julian\Enter a date" ?1 CjCh ;
"_j>: Convert julian to date\Enter a julian day number" ?1 CgCi ;
"_etr: Get Easter for a year\Enter a year or date" ?1 Ck CgCi ;
~
"+: Add n to a date.\Enter date first\Enter n second" ?2 VCjChv+CgCi;
"-: Subtract n from a date\Enter date first\Enter n second" ?2  
VCjChv-CgCi;
"dif: Get the difference\between two dates" ?2 CjChr2CjCh-b ;
"_day: Get the day of the week\Enter a date" ?1 g1 CjCh 7% 
c(
  D'Monday|Ok|' :
  D'Tuesday|Ok|' :
  D'Wednesday|Ok|' :
  D'Thursday|Ok|' :
  D'Friday|Ok|' :
  D'Saturday|Ok|' :
  D'Sunday|Ok|'
)d1 ;