diff --git a/ccpp/CCPP_driver.F90 b/ccpp/CCPP_driver.F90
index bcea940c1..3d4a8e07f 100644
--- a/ccpp/CCPP_driver.F90
+++ b/ccpp/CCPP_driver.F90
@@ -59,6 +59,8 @@ subroutine CCPP_step (step, nblks, ierr)
     ! Local variables
     integer :: nb, nt, ntX
     integer :: ierr2
+    integer :: kdt_iau
+    logical :: iauwindow_center
     ! DH* 20210104 - remove kdt_rad when code to clear diagnostic buckets is removed
     integer :: kdt_rad
 
@@ -167,8 +169,17 @@ subroutine CCPP_step (step, nblks, ierr)
       endif
 
       !--- determine if physics diagnostics buckets need to be cleared
+      iauwindow_center = .false.
+      if (GFS_control%iau_offset > 0) then
+        kdt_iau = nint(GFS_control%iau_offset*3600./GFS_control%dtp)
+        if (GFS_control%kdt-1 == kdt_iau) then
+          iauwindow_center = .true.
+          if( GFS_control%me == 0)print *,'in ccpp step vary, iauwindow_center=',iauwindow_center,&
+            'kdt=',GFS_control%kdt,'dtp=',GFS_control%dtp,'iau_offset=',GFS_control%iau_offset
+        endif
+      endif
       if ((mod(GFS_control%kdt-1,GFS_control%nszero)) == 0) then
-        call GFS_Intdiag%phys_zero(GFS_control)
+        call GFS_Intdiag%phys_zero(GFS_control, iauwindow_center=iauwindow_center)
       endif
 
       !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
diff --git a/fv3/atmos_model.F90 b/fv3/atmos_model.F90
index 0cd5d45e3..690bd74ea 100644
--- a/fv3/atmos_model.F90
+++ b/fv3/atmos_model.F90
@@ -1001,24 +1001,18 @@ subroutine update_atmos_model_state (Atmos, rc)
     call get_time (Atmos%Time - Atmos%Time_init, seconds)
     call atmosphere_nggps_diag(Atmos%Time,ltavg=.true.,avg_max_length=avg_max_length)
     if (ANY(nint(output_fh(:)*3600.0) == seconds) .or. (GFS_control%kdt == first_kdt)) then
-      if (mpp_pe() == mpp_root_pe()) write(6,*) "---isec,seconds",isec,seconds
       time_int = real(isec)
+      time_intfull = real(seconds)
       if(Atmos%iau_offset > zero) then
         if( time_int - Atmos%iau_offset*3600. > zero ) then
           time_int = time_int - Atmos%iau_offset*3600.
-        else if(seconds == Atmos%iau_offset*3600) then
-          call get_time (Atmos%Time - diag_time_fhzero, isec_fhzero)
-          time_int = real(isec_fhzero)
-          if (mpp_pe() == mpp_root_pe()) write(6,*) "---iseczero",isec_fhzero
         endif
-      endif
-      time_intfull = real(seconds)
-      if(Atmos%iau_offset > zero) then
         if( time_intfull - Atmos%iau_offset*3600. > zero) then
           time_intfull = time_intfull - Atmos%iau_offset*3600.
         endif
       endif
-      if (mpp_pe() == mpp_root_pe()) write(6,*) ' gfs diags time since last bucket empty: ',time_int/3600.,'hrs'
+      if (mpp_pe() == mpp_root_pe()) write(6,*) 'gfs diags time since last bucket empty: ',time_int,' time_intfull=', &
+         time_intfull,' kdt=',GFS_control%kdt
       call atmosphere_nggps_diag(Atmos%Time)
       call fv3atm_diag_output(Atmos%Time, GFS_Diag, Atm_block, GFS_control%nx, GFS_control%ny, &
                             GFS_control%levs, 1, 1, 1.0_GFS_kind_phys, time_int, time_intfull, &
diff --git a/fv3/fv3_cap.F90 b/fv3/fv3_cap.F90
index 49f13d0d9..5169ca057 100644
--- a/fv3/fv3_cap.F90
+++ b/fv3/fv3_cap.F90
@@ -949,11 +949,7 @@ subroutine InitializeAdvertise(gcomp, rc)
             if( nfhmax>output_startfh) nfh = nint((nfhmax-output_startfh)/outputfh2(1)) + 1
             if( nfh > 0) then
               allocate(output_fh(nfh))
-              if( output_startfh == 0) then
-                output_fh(1) = dt_atmos/3600.
-              else
-                output_fh(1) = output_startfh
-              endif
+              output_fh(1) = output_startfh + dt_atmos/3600.
               do i=2,nfh
                 output_fh(i) = (i-1)*outputfh2(1) + output_startfh
                 ! Except fh000, which is the first time output, if any other of the