Fortran Wiki
init_seed

This subroutine is from a post on comp.lang.fortran.

subroutine init_seed()
  integer :: n, ival(8), v(3), i
  integer, allocatable :: seed(:)
  call date_and_time(values=ival)
  v(1) = ival(8) + 2048*ival(7)
  v(2) = ival(6) + 64*ival(5)     ! value(4) isn't really 'random'
  v(3) = ival(3) + 32*ival(2) + 32*8*ival(1)
  call random_seed(size=n)
  allocate(seed(n))
  call random_seed()   ! Give the seed an implementation-dependent kick
  call random_seed(get=seed)
  do i=1, n
     seed(i) = seed(i) + v(mod(i-1, 3) + 1)
  enddo
  call random_seed(put=seed)
  deallocate(seed)
end subroutine