Time and Date Functions

Library functions that return the time of day or elapsed CPU time vary from system to system.

The following time functions are not supported directly in the Sun Fortran libraries, but you can write subroutines to duplicate their functions:

• Time-of-day in 10h format

• Date in A10 format

• Milliseconds of job CPU time

• Julian date in ASCII

The time functions supported in the Sun Fortran library are listed in the following table:

Table 7-1 Sun Fortran Time Functions

Name	Function	Man Page
time	Returns the number of seconds elapsed since January, 1, 1970	time(3F)
date	Returns date as a character string	date(3F)
fdate	Returns the current time and date as a character string	fdate(3F)
idate	Returns the current month, day, and year in an integer array	idate(3F)
itime	Returns the current hour, minute, and second in an integer array	itime(3F)
ctime	Converts the time returned by the time function to a character string	ctime(3F)
ltime	Converts the time returned by the time function to the local time	ltime(3F)
gmtime	Converts the time returned by the time function to Greenwich time	gmtime(3F)
etime	Single processor: Returns elapsed user and system time for program execution Multiple processors: Returns the wall clock time	etime(3F)
dtime	Returns the elapsed user and system time since last call to dtime	dtime(3F)
date_and_time	Returns date and time in character and numeric form	date_and_time(3F)

For details, see Fortran Library Reference Manual or the individual man pages for these functions. The routines listed in the following table provide compatibility with VMS Fortran system routines idate and time. To use these routines, you must include the -lV77 option on the f77 command line, in which case you also get these VMS versions instead of the standard f77 versions.

Table 7-2 Summary: Nonstandard VMS Fortran System Routines

Name	Definition	Calling Sequence	Argument Type
idate	Date as day, month, year	call idate( d, m, y )	integer
time	Current time as hhmmss	call time( t )	character*8

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Note -

The date(3F) routine and the VMS version of idate(3F) cannot be Year 2000 safe because they return 2-digit values for the year. Programs that compute time duration by subtracting dates returned by these routines will compute erroneous results after December 31, 1999. The Fortran 90 routine date_and_time(3F) is available for both FORTRAN 77 and Fortran 90 programs, and should be used instead. See the Fortran Library Reference Manual for details.

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The error condition subroutine errsns is not provided, because it is totally specific to the VMS operating system.

Here is a simple example of the use of these time functions (TestTim.f):

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      subroutine startclock 
      common / myclock / mytime 
      integer mytime, time 
      mytime = time() 
      return 
      end 
      function wallclock 
      integer wallclock 
      common / myclock / mytime 
      integer mytime, time, newtime 
      newtime = time() 
      wallclock = newtime - mytime 
      mytime = newtime 
      return 
      end 
      integer wallclock, elapsed 
      character*24 greeting 
      real dtime, timediff, timearray(2) 
c      print a heading 
      call fdate( greeting ) 
      print*,  "      Hello, Time Now Is: ",  greeting 
      print*,      "See how long 'sleep 4' takes, in seconds" 
      call startclock 
      call system( 'sleep 4' ) 
      elapsed = wallclock() 
      print*, "Elapsed time for sleep 4 was: ", elapsed," seconds"
c      now test the cpu time for some trivial computing 
      timediff = dtime( timearray ) 
      q = 0.01 
      do 30 i = 1, 1000 
            q = atan( q ) 
30      continue 
      timediff = dtime( timearray ) 
      print*, "atan(q) 1000 times took: ", timediff ," seconds"
      end 

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Running this program produces the following results:

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demo% TimeTest
       Hello, Time Now Is: Mon Feb 12 11:53:54 1996
 See how long 'sleep 4' takes, in seconds
 Elapsed time for sleep 4 was:   5 seconds
 atan(q) 1000 times took:     2.26550E-03 seconds
demo%

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