diff --git a/src/LIB/SURCOUCHE/src/mode_io_tools_nc4.f90 b/src/LIB/SURCOUCHE/src/mode_io_tools_nc4.f90
index cd5b228fea615e4864956c47f50ef0c2b90f4eb5..ebc79bca7a1483bc397fcf65e98fa46caa69efbc 100644
--- a/src/LIB/SURCOUCHE/src/mode_io_tools_nc4.f90
+++ b/src/LIB/SURCOUCHE/src/mode_io_tools_nc4.f90
@@ -11,6 +11,7 @@
 !  P. Wautelet 10/01/2019: replace handle_err by IO_Err_handle_nc4 for better netCDF error messages
 !  P. Wautelet 05/03/2019: rename IO subroutines and modules
 !  P. Wautelet 18/09/2019: correct support of 64bit integers (MNH_INT=8)
+!  P. Wautelet 14/09/2020: IO_Knowndims_set_nc4: do not store 'time' dimension in diachronic files
 !-----------------------------------------------------------------
 #if defined(MNH_IOCDF4)
 module mode_io_tools_nc4
@@ -274,7 +275,9 @@ IF (TRIM(YPROGRAM)/='PGD' .AND. TRIM(YPROGRAM)/='NESPGD' .AND. TRIM(YPROGRAM)/='
     .AND. .NOT.(TRIM(YPROGRAM)=='REAL' .AND. CSTORAGE_TYPE=='SU') ) THEN !condition to detect PREP_SURFEX
   IF (.NOT. ASSOCIATED(PIOCDF%DIM_LEVEL))   PIOCDF%DIM_LEVEL   => IO_Dimcdf_get_nc4(TPFILE, int( IKU, kind=CDFINT ), 'level')
   IF (.NOT. ASSOCIATED(PIOCDF%DIM_LEVEL_W)) PIOCDF%DIM_LEVEL_W => IO_Dimcdf_get_nc4(TPFILE, int( IKU, kind=CDFINT ), 'level_w')
-  IF (.NOT. ASSOCIATED(PIOCDF%DIMTIME)) PIOCDF%DIMTIME => IO_Dimcdf_get_nc4(TPFILE, NF90_UNLIMITED, 'time')
+  if ( tpfile%ctype /= 'MNHDIACHRONIC' ) then
+    IF (.NOT. ASSOCIATED(PIOCDF%DIMTIME)) PIOCDF%DIMTIME => IO_Dimcdf_get_nc4(TPFILE, NF90_UNLIMITED, 'time')
+  end if
 ELSE
   !PGD and SURFEX files for MesoNH have no vertical levels or time scale
   !These dimensions are allocated to default values
diff --git a/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90 b/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
index 754cebb90e3eda1c9fc809cd420a60be66582391..6a91f4e926b93d0c56e6025b66fb85daaacaa83e 100644
--- a/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
+++ b/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
@@ -19,6 +19,7 @@
 !  P. Wautelet 19/09/2019: temporary workaround for netCDF bug if MNH_INT=8 (if netCDF fortran < 4.4.5)
 !  P. Wautelet 11/02/2020: add 'dims' attribute in IO_Write_field_header_split_nc4
 !  P. Wautelet 25/06/2020: remove workaround for netCDF bug (see 19/09/2019)
+!  P. Wautelet 14/09/2020: IO_Coordvar_write_nc4: do not store 'time' coordinate in diachronic files
 !-----------------------------------------------------------------
 #ifdef MNH_IOCDF4
 module mode_io_write_nc4
@@ -1821,7 +1822,8 @@ END IF
 IF (TPFILE%LMASTER) THEN !Time scale is the same on all processes
   IF (TRIM(YPROGRAM)/='PGD' .AND. TRIM(YPROGRAM)/='NESPGD' .AND. TRIM(YPROGRAM)/='ZOOMPG' &
       .AND. .NOT.(TRIM(YPROGRAM)=='REAL' .AND. CSTORAGE_TYPE=='SU') ) THEN !condition to detect PREP_SURFEX
-    CALL WRITE_TIME_COORD(PIOCDF%DIMTIME)
+    if ( tpfile%ctype /= 'MNHDIACHRONIC' ) &
+      CALL WRITE_TIME_COORD(PIOCDF%DIMTIME)
   END IF
 END IF