diff --git a/src/compo/mopitt_co_nc2ioda.py b/src/compo/mopitt_co_nc2ioda.py
index c247d4df5..bb1374d92 100755
--- a/src/compo/mopitt_co_nc2ioda.py
+++ b/src/compo/mopitt_co_nc2ioda.py
@@ -54,8 +54,9 @@
 
 
 class mopitt(object):
-    def __init__(self, filenames):
+    def __init__(self, filenames, time_range):
         self.filenames = filenames
+        self.time_range = time_range
         self.varDict = defaultdict(lambda: defaultdict(dict))
         self.outdata = defaultdict(lambda: DefaultOrderedDict(OrderedDict))
         self.varAttrs = DefaultOrderedDict(lambda: DefaultOrderedDict(dict))
@@ -151,7 +152,15 @@ def _read(self):
             ap_tc = ap_tc.astype('float32')
 
             # set flag: rule out all anomalous data
-            flg = qa == 0
+            qaf = qa == 0
+
+            # date range to fit DA window
+            date_start = datetime.strptime(self.time_range[0], "%Y%m%d%H")
+            date_end = datetime.strptime(self.time_range[1], "%Y%m%d%H")
+            date_list = [datetime.strptime(date, "%Y-%m-%dT%H:%M:%SZ") for date in times]
+            tsf = [(date_i >= date_start) & (date_i < date_end) for date_i in date_list]
+
+            flg = np.logical_and(qaf, tsf)
 
             if first:
                 # add metadata variables
@@ -230,10 +239,18 @@ def main():
         help="path of IODA output file",
         type=str, required=True)
 
+    optional = parser.add_argument_group(title='optional arguments')
+    optional.add_argument(
+        '-r', '--time_range',
+        help="extract a date range to fit the data assimilation window"
+        "format -r YYYYMMDDHH YYYYMMDDHH",
+        type=str, metavar=('begindate', 'enddate'), nargs=2,
+        default=('1970010100', '2170010100'))
+
     args = parser.parse_args()
 
     # Read in the MOPITT CO data
-    co = mopitt(args.input)
+    co = mopitt(args.input, args.time_range)
 
     # setup the IODA writer
     writer = iconv.IodaWriter(args.output, locationKeyList, DimDict)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 8bbc060ba..5ad87193b 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -893,7 +893,8 @@ ecbuild_add_test( TARGET  test_${PROJECT_NAME}_mopitt_co
                           netcdf
                           "${Python3_EXECUTABLE} ${CMAKE_BINARY_DIR}/bin/mopitt_co_nc2ioda.py
                           -i testinput/mopitt_co.he5
-                          -o testrun/mopitt_co.nc"
+                          -o testrun/mopitt_co.nc
+                          -r 2021092903 2021092921"
                           mopitt_co.nc ${IODA_CONV_COMP_TOL_ZERO})
 
 ecbuild_add_test( TARGET  test_${PROJECT_NAME}_modis_aod
diff --git a/test/testoutput/mopitt_co.nc b/test/testoutput/mopitt_co.nc
index 4a4b12dab..33cccafeb 100644
--- a/test/testoutput/mopitt_co.nc
+++ b/test/testoutput/mopitt_co.nc
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:3a6c239fbb5b72df4ba40a0f3fd534e485569b60f5d4e2e84bc239cd90bd230a
-size 210375
+oid sha256:5a5703deff298e440fb7f4349a4d8585335d16b3d9b9e0e141f4927ac3f42ab4
+size 171846