diff --git a/lib/ft4/ft4d.f90 b/lib/ft4/ft4d.f90
index 13ed8d2cc..7cb1cac01 100644
--- a/lib/ft4/ft4d.f90
+++ b/lib/ft4/ft4d.f90
@@ -54,14 +54,14 @@ program ft4d
 
    do ifile=iarg,nargs
       call getarg(ifile,infile)
-      j2=index(infile,'.wav')
       open(10,file=infile,status='old',access='stream')
       read(10) ihdr
       npts=min(ihdr(11)/2,180000)
       read(10) iwave(1:npts)
       close(10)
-      cdatetime=infile(j2-13:j2)//'000'
-
+      cdatetime=infile
+      j2=index(infile,'.wav')
+      if(j2.ge.14) cdatetime=infile(j2-13:j2)//'000'
       istep=3456
       nsteps=(npts-52800)/istep + 1
       do n=1,nsteps