diff --git a/definitions/mars/grib.efas.an.def b/definitions/mars/grib.efas.an.def
index 4632f6862..10da90a03 100644
--- a/definitions/mars/grib.efas.an.def
+++ b/definitions/mars/grib.efas.an.def
@@ -1,8 +1,13 @@
-# EFAS analysis (water balance)
+# EFAS Analysis (Water Balance)
 alias mars.step = startStep;
 
-alias mars.date = dateOfForecast;
-alias mars.time = timeOfForecast;
+# See ECC-683
+#alias mars.date = dateOfForecast;
+#alias mars.time = timeOfForecast;
+meta valDate validity_date(dataDate,dataTime,endStep,stepUnits): no_copy;
+meta valTime validity_time(dataDate,dataTime,endStep,stepUnits): no_copy;
+alias mars.date = valDate;
+alias mars.time = valTime;
 
 #meta efas_suite_name sprintf("%s_%s_%s", inputOriginatingCentre, efas_forecast, efas_post_proc) : no_copy;
 alias mars.origin = inputOriginatingCentre;
diff --git a/definitions/mars/grib.efas.go.def b/definitions/mars/grib.efas.go.def
index 0b56d2c73..6cfa297c6 100644
--- a/definitions/mars/grib.efas.go.def
+++ b/definitions/mars/grib.efas.go.def
@@ -1,8 +1,13 @@
 # EFAS Gridded observations
 alias mars.step = startStep;
 
-alias mars.date = dateOfForecast;
-alias mars.time = timeOfForecast;
+# See ECC-683
+#alias mars.date = dateOfForecast;
+#alias mars.time = timeOfForecast;
+meta valDate validity_date(dataDate,dataTime,endStep,stepUnits): no_copy;
+meta valTime validity_time(dataDate,dataTime,endStep,stepUnits): no_copy;
+alias mars.date = valDate;
+alias mars.time = valTime;
 
 alias mars.origin = inputOriginatingCentre;