diff --git a/gcm_forecast.tmpl b/gcm_forecast.tmpl
index 6acf75ed..6f2bf7da 100755
--- a/gcm_forecast.tmpl
+++ b/gcm_forecast.tmpl
@@ -749,6 +749,26 @@ if( $REPLAY_MODE == 'Exact' | $REPLAY_MODE == 'Regular' ) then
 
 endif
 
+# Update GAAS_GridComp_ExtData.yaml with CHEMISTRY_DT
+# ---------------------------------------------------
+
+# NOTE: Even though GAAS is disabled above, we keep this code here in case this changes
+
+# We need to make sure GAAS has an offset that matches CHEMISTRY_DT from CAP.rc
+# We also need to take that CHEMISTRY_DT and convert it to ISO duration format in seconds
+# So, if CHEMISTRY_DT is 1800, we need to convert it to PT1800S
+# Then in GAAS_GridComp_ExtData.yaml, we need to find:
+#     update_offset: PT450S
+# and replace it with:
+#     update_offset: PT1800S
+# NOTE: Since it is YAML, we need to make sure the indentation is correct
+# 1. First we grab the CHEMISTRY_DT from CAP.rc
+set CAPRC_CHEMISTRY_DT = `grep '^\s*CHEMISTRY_DT:' CAP.rc | cut -d: -f2 | awk '{print $1}'`
+# 2. Then we convert it to ISO duration format
+set CHEMDT_ISO_DURATION = `echo "PT${CAPRC_CHEMISTRY_DT}S"`
+# 3. Then we replace the update_offset in GAAS_GridComp_ExtData.yaml
+sed -i "s/update_offset: .*/update_offset: ${CHEMDT_ISO_DURATION}/" GAAS_GridComp_ExtData.yaml
+
 # Establish safe default number of OpenMP threads
 # -----------------------------------------------
 setenv OMP_NUM_THREADS 1
diff --git a/gcm_run.j b/gcm_run.j
index 3c91ad40..586e518e 100755
--- a/gcm_run.j
+++ b/gcm_run.j
@@ -970,6 +970,24 @@ if( $REPLAY_MODE == 'Exact' | $REPLAY_MODE == 'Regular' ) then
 
 endif
 
+# Update GAAS_GridComp_ExtData.yaml with CHEMISTRY_DT
+# ---------------------------------------------------
+
+# We need to make sure GAAS has an offset that matches CHEMISTRY_DT from CAP.rc
+# We also need to take that CHEMISTRY_DT and convert it to ISO duration format in seconds
+# So, if CHEMISTRY_DT is 1800, we need to convert it to PT1800S
+# Then in GAAS_GridComp_ExtData.yaml, we need to find:
+#     update_offset: PT450S
+# and replace it with:
+#     update_offset: PT1800S
+# NOTE: Since it is YAML, we need to make sure the indentation is correct
+# 1. First we grab the CHEMISTRY_DT from CAP.rc
+set CAPRC_CHEMISTRY_DT = `grep '^\s*CHEMISTRY_DT:' CAP.rc | cut -d: -f2 | awk '{print $1}'`
+# 2. Then we convert it to ISO duration format
+set CHEMDT_ISO_DURATION = `echo "PT${CAPRC_CHEMISTRY_DT}S"`
+# 3. Then we replace the update_offset in GAAS_GridComp_ExtData.yaml
+sed -i "s/update_offset: .*/update_offset: ${CHEMDT_ISO_DURATION}/" GAAS_GridComp_ExtData.yaml
+
 # Establish safe default number of OpenMP threads
 # -----------------------------------------------
 @MIT # ---------------------------------------------------
diff --git a/gcm_run_benchmark.j b/gcm_run_benchmark.j
index 0b87eb2c..8fcc6eb4 100755
--- a/gcm_run_benchmark.j
+++ b/gcm_run_benchmark.j
@@ -827,6 +827,9 @@ if( $REPLAY_MODE == 'Exact' | $REPLAY_MODE == 'Regular' ) then
 
      # Modify GAAS_GridComp.rc and Link REPLAY files
      # ---------------------------------------------
+     /bin/mv -f GAAS_GridComp_ExtData.yaml GAAS_GridComp_ExtData.yaml.tmpl
+     cat GAAS_GridComp_ExtData.yaml.tmpl | sed -e "s?das.aod_?chem/Y%y4/M%m2/${ANA_EXPID}.aod_?g" > GAAS_GridComp_ExtData.yaml
+
      /bin/mv -f GAAS_GridComp.rc GAAS_GridComp.tmp
      cat GAAS_GridComp.tmp | sed -e "s?aod/Y%y4/M%m2/${ANA_EXPID}.?aod/Y%y4/M%m2/${ANA_EXPID}.?g" > GAAS_GridComp.rc
 
@@ -836,6 +839,24 @@ if( $REPLAY_MODE == 'Exact' | $REPLAY_MODE == 'Regular' ) then
 
 endif
 
+# Update GAAS_GridComp_ExtData.yaml with CHEMISTRY_DT
+# ---------------------------------------------------
+
+# We need to make sure GAAS has an offset that matches CHEMISTRY_DT from CAP.rc
+# We also need to take that CHEMISTRY_DT and convert it to ISO duration format in seconds
+# So, if CHEMISTRY_DT is 1800, we need to convert it to PT1800S
+# Then in GAAS_GridComp_ExtData.yaml, we need to find:
+#     update_offset: PT450S
+# and replace it with:
+#     update_offset: PT1800S
+# NOTE: Since it is YAML, we need to make sure the indentation is correct
+# 1. First we grab the CHEMISTRY_DT from CAP.rc
+set CAPRC_CHEMISTRY_DT = `grep '^\s*CHEMISTRY_DT:' CAP.rc | cut -d: -f2 | awk '{print $1}'`
+# 2. Then we convert it to ISO duration format
+set CHEMDT_ISO_DURATION = `echo "PT${CAPRC_CHEMISTRY_DT}S"`
+# 3. Then we replace the update_offset in GAAS_GridComp_ExtData.yaml
+sed -i "s/update_offset: .*/update_offset: ${CHEMDT_ISO_DURATION}/" GAAS_GridComp_ExtData.yaml
+
 # Establish safe default number of OpenMP threads
 # -----------------------------------------------
 setenv OMP_NUM_THREADS 1