diff --git a/cime_config/buildnml b/cime_config/buildnml
index 674d1a29ea..01253a0e7d 100755
--- a/cime_config/buildnml
+++ b/cime_config/buildnml
@@ -47,6 +47,23 @@ def buildnml(case, caseroot, compname):
     RUN_REFDATE         = case.get_value("RUN_REFDATE")
     RUN_REFTOD          = case.get_value("RUN_REFTOD")
     COMP_INTERFACE      = case.get_value("COMP_INTERFACE")
+    CALENDAR            = case.get_value("CALENDAR")
+    COMPSET             = case.get_value("COMPSET")
+ 
+# The Gregorian calendar currently can't be used with spinup compsets
+# because CAM's stream-handling code can't handle a request for data
+# for Feb 29 (possibly specified in a leapday testmod) from a non-leap-year
+# in the stream(s) data (specified in a use_case, e.g. 1850_cam_lt.xml).
+# This limitation can be removed when CAM's stream-handling is switched to
+# using CDEPS, which appears to handle this situation. (See discussion in
+# https://github.com/ESCOMP/CAM/issues/1447 for details.)
+    if CALENDAR.startswith("GREGORIAN"):
+        spinup_po = re.compile('\d{4}')
+        spinup = spinup_po.match(COMPSET)
+        expect(spinup == None,
+            "Gregorian calendar (modifier _cG) cannot be used with spinup compset \n  {}".format(COMPSET)
+        )
+
 
     testsrc = os.path.join(srcroot, "components", "cam")
     if os.path.exists(testsrc):
diff --git a/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/shell_commands b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/shell_commands
index 2805059fe3..5d2ba4457f 100644
--- a/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/shell_commands
+++ b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/shell_commands
@@ -3,4 +3,4 @@ if [ "$driver" = "nuopc" ]; then
   ./xmlchange ROF_NCPL=\$ATM_NCPL
   ./xmlchange GLC_NCPL=\$ATM_NCPL
 fi
-./xmlchange RUN_STARTDATE=2012-02-29
+./xmlchange RUN_STARTDATE=2008-02-29
diff --git a/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_cice b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_cice
new file mode 100644
index 0000000000..25175d22d4
--- /dev/null
+++ b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_cice
@@ -0,0 +1,8 @@
+!----------------------------------------------------------------------------------
+! Users should add all user specific namelist changes below in the form of 
+!   namelist_var = new_namelist_value 
+! Note - that it does not matter what namelist group the namelist_var belongs to
+!----------------------------------------------------------------------------------
+histfreq   = 'd'
+histfreq_n = 1
+ 
diff --git a/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_clm b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_clm
index 0d83b5367b..da794cc283 100644
--- a/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_clm
+++ b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_clm
@@ -24,4 +24,5 @@
 hist_nhtfrq = 9
 hist_mfilt  = 1
 hist_ndens  = 1
-
+check_finidat_year_consistency = .false.
+for_testing_allow_non_annual_changes = .true.
diff --git a/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_mosart b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_mosart
new file mode 100644
index 0000000000..3f64f4bb96
--- /dev/null
+++ b/cime_config/testdefs/testmods_dirs/cam/outfrq9s_leapday/user_nl_mosart
@@ -0,0 +1,8 @@
+!----------------------------------------------------------------------------------
+! Users should add all user specific namelist changes below in the form of 
+! namelist_var = new_namelist_value 
+! NOTE: namelist variable delt_mosart (the time-step) CAN ONLY be changed by modifying the value
+!       of the xml variable ROF_NCPL in env_run.xml
+!----------------------------------------------------------------------------------
+nhtfrq = -24
+