CALL SEQUENCE...
         tstep  IN OUT INPUT OUTPUT [-a VAL1 -b VAL2 -kind VAL3]
 
 
      DESCRIPTION...
       tstep  - RELABELS MODEL TIMESTEP NUMBER TO DATE-TIME GROUP.
 
 
      AUTHORS - S.Lambert, E.Chan, MARCH 01/1993.
      LAST REVISION: $Header: /home/cvs/RMNLIB/utils/rdiag/lspgm/tstep.ptn,v 4.12 2014/09/25 20:20:55 dugas Exp $
 
 
      PURPOSE - CHANGES THE MODEL TIMESTEP NUMBER IN IBUF(2) TO ONE OF THE
                SUPPORTED DATE-TIME FORMATS, A DATE AND TIME CORRESPONDING
                TO THE BEGINNING OF THE MODEL RUN MAY BE SPECIFIED ON THE
                INPUT CARD, OTHERWISE JAN 1 00Z OF YEAR 1901 IS ASSUMED.
 
 
      INPUT FILE...
       IN     = INPUT FILE WITH MODEL TIMESTEP NUMBERS IN IBUF(2).
                PLEASE NOTE THAT TIMESTEP SHOULD ALL HAVE THE SAME
                NUMBER OF LEVELS AND VARIABLES
 
      OUTPUT FILE...
       OUT    = COPY OF IN WITH 2ND WORD OF THE 8-WORD LABEL CHANGED
                                                                            
 
      INPUT PARAMETERS... 
       MSTEP  (a) = NUMBER OF MINUTES PER MODEL TIMESTEP
       MSTART (b) = STARTING DATE AND TIME OF THE MODEL RUN IN THE
                    FORMAT SPECIFIED BY THE DTM PARAMETER. OTHERWISE,
                    JAN 1 00Z OF YEAR 1901 IS ASSUMED.
       DTM (kind) = FLAG TO INDICATE METHOD OF TIME MEASUREMENT.
                  = 0,1 ==> IBUF(2) WILL BE IN THE FORMAT YYYYMMDDHH
                  = 2   ==> IBUF(2) WILL BE IN THE FORMAT YYYYMMDDHHMM
                  = 3   ==> IBUF(2) WILL BE IN THE FORMAT YYYYMMDDHH. BUT
                            NOW, LEAP YEARS ARE TAKEN INTO ACCOUNT.
                  = 4   ==> IBUF(2) IS SIMPLY THE ORDINAL OF THE
                            TIMESTEP IN THE FILE
 
 
      Note:   - An IBUF(2) value will be recognized as a timestep if it
                a positive number smaller than 30 01 01 00. Larger values
                are assumed to already be in a particular time format.
                This number of steps corresponds to about 570 years,
                assuming 10 minute timesteps.
 
 
       READ(5,5010) MSTEP,MSTART,DTM
 5010  FORMAT(10X,I5,I15,I5)
 
 
      EXAMPLE OF INPUT CARD...
 
  TSTEP      20       79070112    0
 
         0123456789012345678901234567890123456789012345678901234567890
         1         2         3         4         5         6         7
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 PROBLEM DECODING MSTART
        2 UNABLE TO READ FIRST TIMESTEP
        3 PROBLEM WHILE READING DIRECTIVES
        4 UNABLE TO ALLOCATE ENOUGH WORKING MEMORY
        5 IBUF(2) IS NOT RECOGNIZED AS A TIMESTEP