Julian Day to Julian or Gregorian Calendar Date.

Adapted from a May 1984 Sky & Telescope article.

This example is given in my March 2000 Sky & Telescope article.

Enter Julian Day: (integer part) (fractional part)
Select Julian or Gregorian Calendar:
Calendar Date (Year, Month, Day):

Here's the original code for comparison with the ECMAScript code (e.g. see jdToCalendar()):
   900 REM   JD --> CALENDAR
   905 REM
   910 INPUT "J,F ";J,F
   915 INPUT "JC (0) OR GC (1) ";G
   920 F=F+0.5
   925 IF F<1 THEN 935
   930 F=F-1: J=J+1
   935 IF G=1 THEN 945
   940 A=J: GOTO 955
   945 A1=INT((J/36524.25)-51.12264)
   950 A=J+1+A1-INT(A1/4)
   955 B=A+1524
   960 C=INT((B/365.25)-0.3343)
   965 D=INT(365.25*C)
   970 E=INT((B-D)/30.61)
   975 D=B-D-INT(30.61*E)+F
   980 M=E-1: Y=C-4716
   985 IF E>13.5 THEN M=M-12
   990 IF M<2.5 THEN Y=Y+1
   995 PRINT "DATE: ";Y;M;D
   997 END
   1000 REM  ------------------------
   1001 REM  APPEARED IN ASTRONOMICAL
   1002 REM  COMPUTING, SKY & TELE-
   1003 REM  SCOPE, MAY, 1984
   1004 REM  ------------------------