diff --git a/docs/source/operations/transformations/vgridshift.rst b/docs/source/operations/transformations/vgridshift.rst
index ca2b421c17..a48c2ac3ba 100644
--- a/docs/source/operations/transformations/vgridshift.rst
+++ b/docs/source/operations/transformations/vgridshift.rst
@@ -11,9 +11,11 @@ Change Vertical datum change by grid shift
 +-----------------+--------------------------------------------------------------------+
 | **Domain**      | 3D                                                                 |
 +-----------------+--------------------------------------------------------------------+
-| **Input type**  | Geodetic coordinates (horizontal), meters (vertical).              |
+| **Input type**  | Geodetic coordinates (horizontal), meters (vertical),              |
+|                 | decimalyear (temporal)                                             |
 +-----------------+--------------------------------------------------------------------+
-| **Output type** | Geodetic coordinates (horizontal), meters (vertical).              |
+| **Output type** | Geodetic coordinates (horizontal), meters (vertical),              |
+|                 | decimalyear (temporal)                                             |
 +-----------------+--------------------------------------------------------------------+
 
 The vertical grid shift is done by offsetting the vertical input coordinates by
@@ -50,3 +52,7 @@ Parameters
     not available.
 
     Grids are expected to be in GTX format.
+
+.. option:: +t_final=<time>
+
+.. option:: +t_epoch=<time>
diff --git a/src/PJ_hgridshift.c b/src/PJ_hgridshift.c
index 3932ef51d7..dddf0413b4 100644
--- a/src/PJ_hgridshift.c
+++ b/src/PJ_hgridshift.c
@@ -1,12 +1,20 @@
 #define PJ_LIB__
 
+#include <errno.h>
+#include <string.h>
 #include <stddef.h>
+#include <time.h>
 
 #include "proj_internal.h"
 #include "projects.h"
 
 PROJ_HEAD(hgridshift, "Horizontal grid shift");
 
+struct pj_opaque_hgridshift {
+    double t_final;
+    double t_epoch;
+};
+
 static XYZ forward_3d(LPZ lpz, PJ *P) {
     PJ_COORD point = {{0,0,0,0}};
     point.lpz = lpz;
@@ -34,21 +42,36 @@ static LPZ reverse_3d(XYZ xyz, PJ *P) {
     return point.lpz;
 }
 
-
-static PJ_COORD forward_4d (PJ_COORD obs, PJ *P) {
-    obs.xyz = forward_3d (obs.lpz, P);
-    return obs;
+static PJ_COORD forward_4d(PJ_COORD obs, PJ *P) {
+    struct pj_opaque_hgridshift *Q = (struct pj_opaque_hgridshift *) P->opaque;
+    PJ_COORD point = obs;
+    if (Q->t_final != 0.0  && Q->t_epoch != 0.0) {
+        if (obs.lpzt.t < Q->t_epoch && Q->t_final > Q->t_epoch)
+            point.xyz = forward_3d (obs.lpz, P);
+    } else {
+        point.xyz = forward_3d (obs.lpz, P);
+    }
+    return point;
 }
 
-
-static PJ_COORD reverse_4d (PJ_COORD obs, PJ *P) {
-    obs.lpz = reverse_3d (obs.xyz, P);
-    return obs;
+static PJ_COORD reverse_4d(PJ_COORD obs, PJ *P) {
+    struct pj_opaque_hgridshift *Q = (struct pj_opaque_hgridshift *) P->opaque;
+    PJ_COORD point = obs;
+    if (Q->t_final != 0.0  && Q->t_epoch != 0.0) {
+        if (obs.lpzt.t < Q->t_epoch && Q->t_final > Q->t_epoch)
+            point.lpz = reverse_3d (obs.xyz, P);
+    } else {
+        point.lpz = reverse_3d (obs.xyz, P);
+    }
+    return point;
 }
 
 
-
 PJ *TRANSFORMATION(hgridshift,0) {
+    struct pj_opaque_hgridshift *Q = pj_calloc (1, sizeof (struct pj_opaque_hgridshift));
+    if (0==Q)
+        return pj_default_destructor (P, ENOMEM);
+    P->opaque = (void *) Q;
 
     P->fwd4d  = forward_4d;
     P->inv4d  = reverse_4d;
@@ -65,6 +88,24 @@ PJ *TRANSFORMATION(hgridshift,0) {
         return pj_default_destructor (P, PJD_ERR_NO_ARGS);
     }
 
+   if (pj_param(P->ctx, P->params, "tt_final").i) {
+        Q->t_final = pj_param (P->ctx, P->params, "dt_final").f;
+        if (Q->t_final == 0) {
+            /* a number wasn't passed to +t_final, let's see if it was "now" */
+            /* and set the time accordingly.                                 */
+            if (!strcmp("now", pj_param(P->ctx, P->params, "st_final").s)) {
+                    time_t now;
+                    struct tm *date;
+                    time(&now);
+                    date = localtime(&now);
+                    Q->t_final = 1900.0 + date->tm_year + date->tm_yday/365.0;
+            }
+        }
+    }
+
+   if (pj_param(P->ctx, P->params, "tt_epoch").i)
+        Q->t_epoch = pj_param (P->ctx, P->params, "dt_epoch").f;
+
 
     proj_hgrid_init(P, "grids");
     /* Was gridlist compiled properly? */
diff --git a/src/PJ_vgridshift.c b/src/PJ_vgridshift.c
index 205806b2eb..6def926b34 100644
--- a/src/PJ_vgridshift.c
+++ b/src/PJ_vgridshift.c
@@ -1,12 +1,19 @@
 #define PJ_LIB__
 
+#include <errno.h>
 #include <stddef.h>
+#include <string.h>
+#include <time.h>
 
 #include "proj_internal.h"
 #include "projects.h"
 
 PROJ_HEAD(vgridshift, "Vertical grid shift");
 
+struct pj_opaque_vgridshift {
+    double t_final;
+    double t_epoch;
+};
 
 static XYZ forward_3d(LPZ lpz, PJ *P) {
     PJ_COORD point = {{0,0,0,0}};
@@ -37,25 +44,60 @@ static LPZ reverse_3d(XYZ xyz, PJ *P) {
 
 
 static PJ_COORD forward_4d(PJ_COORD obs, PJ *P) {
-    PJ_COORD point = {{0,0,0,0}};
-    point.xyz = forward_3d (obs.lpz, P);
+    struct pj_opaque_vgridshift *Q = (struct pj_opaque_vgridshift *) P->opaque;
+    PJ_COORD point = obs;
+    if (Q->t_final != 0.0  && Q->t_epoch != 0.0) {
+        if (obs.lpzt.t < Q->t_epoch && Q->t_final > Q->t_epoch)
+            point.xyz = forward_3d (obs.lpz, P);
+    } else {
+        point.xyz = forward_3d (obs.lpz, P);
+    }
     return point;
 }
 
 static PJ_COORD reverse_4d(PJ_COORD obs, PJ *P) {
-    PJ_COORD point;
-    point.lpz = reverse_3d (obs.xyz, P);
+    struct pj_opaque_vgridshift *Q = (struct pj_opaque_vgridshift *) P->opaque;
+    PJ_COORD point = obs;
+    if (Q->t_final != 0.0  && Q->t_epoch != 0.0) {
+        if (obs.lpzt.t < Q->t_epoch && Q->t_final > Q->t_epoch)
+            point.lpz = reverse_3d (obs.xyz, P);
+    } else {
+        point.lpz = reverse_3d (obs.xyz, P);
+    }
     return point;
 }
 
 
 PJ *TRANSFORMATION(vgridshift,0) {
+    struct pj_opaque_vgridshift *Q = pj_calloc (1, sizeof (struct pj_opaque_vgridshift));
+    if (0==Q)
+        return pj_default_destructor (P, ENOMEM);
+    P->opaque = (void *) Q;
 
    if (!pj_param(P->ctx, P->params, "tgrids").i) {
         proj_log_error(P, "vgridshift: +grids parameter missing.");
         return pj_default_destructor(P, PJD_ERR_NO_ARGS);
     }
 
+   if (pj_param(P->ctx, P->params, "tt_final").i) {
+        Q->t_final = pj_param (P->ctx, P->params, "dt_final").f;
+        if (Q->t_final == 0) {
+            /* a number wasn't passed to +t_final, let's see if it was "now" */
+            /* and set the time accordingly.                                 */
+            if (!strcmp("now", pj_param(P->ctx, P->params, "st_final").s)) {
+                    time_t now;
+                    struct tm *date;
+                    time(&now);
+                    date = localtime(&now);
+                    Q->t_final = 1900.0 + date->tm_year + date->tm_yday/365.0;
+            }
+        }
+    }
+
+   if (pj_param(P->ctx, P->params, "tt_epoch").i)
+        Q->t_epoch = pj_param (P->ctx, P->params, "dt_epoch").f;
+
+
     /* Build gridlist. P->vgridlist_geoid can be empty if +grids only ask for optional grids. */
     proj_vgrid_init(P, "grids");
 
diff --git a/test/gie/deformation.gie b/test/gie/deformation.gie
index b6ca3e0f10..22c9388767 100644
--- a/test/gie/deformation.gie
+++ b/test/gie/deformation.gie
@@ -62,4 +62,77 @@ expect      failure pjd_err_failed_to_load_grid
 
 operation   proj=deformation xy_grids=alaska z_grids=nonexisting ellps=GRS80
 expect      failure pjd_err_missing_args
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=egm96_15.gtx +t_epoch=2010.0 +t_final=2018.0
+-------------------------------------------------------------------------------
+tolerance 0.1 mm
+ignore      pjd_err_failed_to_load_grid
+
+accept      12 56  0.0        2000.0
+expect      12 56 -36.5966    2000.0
+
+accept      12 56  0.0        2011.0
+expect      12 56  0.0        2011.0
+
+accept      12 56  0.0        2019.0
+expect      12 56  0.0        2019.0
+
+accept      12 56  0.0
+expect      12 56 -36.5966
+
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=egm96_15.gtx +t_epoch=2010.0 +t_final=now
+-------------------------------------------------------------------------------
+tolerance 0.1 mm
+ignore      pjd_err_failed_to_load_grid
+
+accept      12 56  0.0        2000.0
+expect      12 56 -36.5966    2000.0
+
+accept      12 56  0.0        2011.0
+expect      12 56  0.0        2011.0
+
+accept      12 56  0.0        3011.0
+expect      12 56  0.0        3011.0
+
+
+-------------------------------------------------------------------------------
+operation +proj=hgridshift +grids=alaska +t_epoch=2010.0 +t_final=2018.0
+-------------------------------------------------------------------------------
+tolerance 0.1 mm
+ignore      pjd_err_failed_to_load_grid
+
+accept      -147.0              64.0                0.0     2000.0
+expect      -147.0023233121     63.9995792119       0.0     2000.0
+roundtrip   100
+
+accept      -147.0              64.0                0.0     2011.0
+expect      -147.0              64.0                0.0     2011.0
+roundtrip   100
+
+accept      -147.0              64.0                0.0     2011.0
+expect      -147.0              64.0                0.0     2020.0
+roundtrip   100
+
+-------------------------------------------------------------------------------
+operation +proj=hgridshift +grids=alaska +t_epoch=2010.0 +t_final=now
+-------------------------------------------------------------------------------
+tolerance 0.1 mm
+ignore      pjd_err_failed_to_load_grid
+
+accept      -147.0              64.0                0.0     2000.0
+expect      -147.0023233121     63.9995792119       0.0     2000.0
+roundtrip   100
+
+accept      -147.0              64.0                0.0     2011.0
+expect      -147.0              64.0                0.0     2011.0
+roundtrip   100
+
+accept      -147.0              64.0                0.0     3011.0
+expect      -147.0              64.0                0.0     3011.0
+roundtrip   100
+
+
 </gie>