diff --git a/compliance_checker/cf/util.py b/compliance_checker/cf/util.py
index 9443eb33..03bdefe1 100644
--- a/compliance_checker/cf/util.py
+++ b/compliance_checker/cf/util.py
@@ -8,9 +8,13 @@
 from importlib_resources import files
 from lxml import etree
 from netCDF4 import Dataset
+from pyudunits2 import UnitSystem
+from pyudunits2._exceptions import UnresolvableUnitException
 
 from compliance_checker.cfutil import units_convertible
 
+ut_system = UnitSystem.from_udunits2_xml()
+
 # copied from paegan
 # paegan may depend on these later
 _possiblet = {
@@ -321,16 +325,27 @@ def create_cached_data_dir():
 
 def units_known(units):
     try:
+        # FIXME: pyudnits2 fails with dates.
+        #   File "inline", line 1
+        #     'seconds since 1970-01-01T00:00:00Z'
+        #                                 ^^^^^^^^
+        # SyntaxError: mismatched input ':' expecting <EOF>
+        # ut_system.unit(units)
         Unit(units)
-    except ValueError:
+    except (ValueError, UnresolvableUnitException):
         return False
     return True
 
 
 def units_temporal(units):
     try:
+        # FIXME: pyudnits2 fails with dates.
+        #   File "inline", line 1
+        #     'seconds since 1970-01-01T00:00:00Z'
+        #                                 ^^^^^^^^
+        # SyntaxError: mismatched input ':' expecting <EOF>
         u = Unit(units)
-    except ValueError:
+    except (ValueError, UnresolvableUnitException):
         return False
     # IMPLEMENTATION CONFORMANCE REQUIRED 4.4 1/3
     # time units of a time_coordinate variable must contain a reference
@@ -403,21 +418,22 @@ def compare_unit_types(specified, reference):
     msgs = []
     err_flag = False
     try:
-        specified_unit = Unit(specified)
-    except ValueError:
+        specified_unit = ut_system.unit(specified)
+    except UnresolvableUnitException:
         msgs.append(f"Specified conversion unit f{specified} may not be valid UDUnits")
         err_flag = True
 
     try:
-        reference_unit = Unit(reference)
-    except ValueError:
+        reference_unit = ut_system.unit(reference)
+    except UnresolvableUnitException:
         msgs.append(f"Specified conversion unit f{reference} may not be valid UDUnits")
         err_flag = True
 
     if err_flag:
         return msgs
 
-    unit_convertible = specified_unit.is_convertible(reference_unit)
+    # FIXME: This one passed with the wrong syntax!! Our tests are probably not covering this!!!
+    unit_convertible = specified_unit.is_convertible_to(reference_unit)
     fail_msg = [f'Units "{specified}" are not convertible to "{reference}"']
     return msgs if unit_convertible else fail_msg
 
diff --git a/compliance_checker/cfutil.py b/compliance_checker/cfutil.py
index 8bcce331..d45f63c9 100644
--- a/compliance_checker/cfutil.py
+++ b/compliance_checker/cfutil.py
@@ -10,6 +10,9 @@
 
 from cf_units import Unit
 from importlib_resources import files
+from pyudunits2 import UnitSystem
+
+ut_system = UnitSystem.from_udunits2_xml()
 
 _UNITLESS_DB = None
 _SEA_NAMES = None
@@ -111,7 +114,9 @@ def is_dimensionless_standard_name(standard_name_table, standard_name):
         f".//entry[@id='{standard_name}']",
     )
     if found_standard_name is not None:
-        canonical_units = Unit(found_standard_name.find("canonical_units").text)
+        canonical_units = ut_system.unit(
+            found_standard_name.find("canonical_units").text,
+        )
         return canonical_units.is_dimensionless()
     # if the standard name is not found, assume we need units for the time being
     else: