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+.help dd2tf Jun99 "Slalib Package"
+.nf
+
+      SUBROUTINE slDDTF (NDP, DAYS, SIGN, IHMSF)
+
+     - - - - - -
+      D D T F
+     - - - - - -
+
+  Convert an interval in days into hours, minutes, seconds
+  (double precision)
+
+  Given:
+     NDP      i      number of decimal places of seconds
+     DAYS     d      interval in days
+
+  Returned:
+     SIGN     c      '+' or '-'
+     IHMSF    i(4)   hours, minutes, seconds, fraction
+
+  Notes:
+
+     1)  NDP less than zero is interpreted as zero.
+
+     2)  The largest useful value for NDP is determined by the size
+         of DAYS, the format of DOUBLE PRECISION floating-point numbers
+         on the target machine, and the risk of overflowing IHMSF(4).
+         For example, on the VAX, for DAYS up to 1D0, the available
+         floating-point precision corresponds roughly to NDP=12.
+         However, the practical limit is NDP=9, set by the capacity of
+         the 32-bit integer IHMSF(4).
+
+     3)  The absolute value of DAYS may exceed 1D0.  In cases where it
+         does not, it is up to the caller to test for and handle the
+         case where DAYS is very nearly 1D0 and rounds up to 24 hours,
+         by testing for IHMSF(1)=24 and setting IHMSF(1-4) to zero.
+
+  P.T.Wallace   Starlink   19 March 1999
+
+  Copyright (C) 1999 Rutherford Appleton Laboratory
+  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
+
+.fi
+.endhelp