anchor.diff:                opt = 1
             elseif (tag(1:5).eq.'-date') then
                 opt = 2
  +          elseif (tag(1:5).eq.'-nsec') then
  +              opt = 3
             elseif (tag(1:5).eq.'-long') then
                 long = 1
             elseif (tag(1:2).eq.'-c') then
  
positive.code:               read(arg1(11:12),*) mn1
                read(arg1(13:14),*) sc1
            endif
            if (opt.eq.1) then
                read(arg2(1:4),*) yr2
                read(arg2(5:6),*) mo2
                read(arg2(7:8),*) dy2
  
negative.code:               read(arg2,*) ndy
            endif
        endif
        if (opt.eq.1.or.opt.eq.3.and.long.eq.1) then
            dy1 = dy1 + hr1/2.4d1 + mn1/1.44d3 + sc1/8.64d4
            dy2 = dy2 + hr2/2.4d1 + mn2/1.44d3 + sc2/8.64d4
        endif
  