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diff --git a/src/slalib/dd2tf.f b/src/slalib/dd2tf.f
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+      SUBROUTINE sla_DD2TF (NDP, DAYS, SIGN, IHMSF)
+*+
+*     - - - - - -
+*      D D 2 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
+*-
+
+      IMPLICIT NONE
+
+      INTEGER NDP
+      DOUBLE PRECISION DAYS
+      CHARACTER SIGN*(*)
+      INTEGER IHMSF(4)
+
+*  Days to seconds
+      DOUBLE PRECISION D2S
+      PARAMETER (D2S=86400D0)
+
+      INTEGER NRS,N
+      DOUBLE PRECISION RS,RM,RH,A,AH,AM,AS,AF
+
+
+
+*  Handle sign
+      IF (DAYS.GE.0D0) THEN
+         SIGN='+'
+      ELSE
+         SIGN='-'
+      END IF
+
+*  Field units in terms of least significant figure
+      NRS=1
+      DO N=1,NDP
+         NRS=NRS*10
+      END DO
+      RS=DBLE(NRS)
+      RM=RS*60D0
+      RH=RM*60D0
+
+*  Round interval and express in smallest units required
+      A=ANINT(RS*D2S*ABS(DAYS))
+
+*  Separate into fields
+      AH=AINT(A/RH)
+      A=A-AH*RH
+      AM=AINT(A/RM)
+      A=A-AM*RM
+      AS=AINT(A/RS)
+      AF=A-AS*RS
+
+*  Return results
+      IHMSF(1)=MAX(NINT(AH),0)
+      IHMSF(2)=MAX(MIN(NINT(AM),59),0)
+      IHMSF(3)=MAX(MIN(NINT(AS),59),0)
+      IHMSF(4)=MAX(NINT(MIN(AF,RS-1D0)),0)
+
+      END