diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 09f68ac2bb..c2e3f7d2b3 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -36,7 +36,7 @@ Added
 * Add ``ST2_USE_DEBUGGER`` env var as alternative to the ``--use-debugger`` cli flag. #5675
   Contributed by @cognifloyd
 
-* Added purging of old tokens. #56791
+* Added purging of old tokens. #5679
   Contributed by Amanda McGuinness (@amanda11 intive)
 
 Changed
@@ -87,6 +87,10 @@ Changed
 
   Contributed by @cognifloyd
 
+* Move from udatetime to ciso8601 for date functionality ahead of supporting python3.9 #5692
+  Contributed by Amanda McGuinness (@amanda11 intive)
+
+
 Removed
 ~~~~~~~
 
diff --git a/fixed-requirements.txt b/fixed-requirements.txt
index ef087fd789..306570a89c 100644
--- a/fixed-requirements.txt
+++ b/fixed-requirements.txt
@@ -82,4 +82,3 @@ psutil==5.8.0
 python-dateutil==2.8.1
 python-statsd==2.1.0
 orjson==3.5.2
-udatetime==0.0.16
diff --git a/requirements.txt b/requirements.txt
index 50e7cb7f01..3d5395bb0f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -13,6 +13,7 @@ argcomplete==1.12.2
 bcrypt==3.2.0
 cffi<1.15.0
 chardet<3.1.0
+ciso8601
 cryptography==3.4.7
 decorator==4.4.2
 dnspython>=1.16.0,<2.0.0
@@ -73,7 +74,6 @@ stevedore==1.30.1
 tenacity>=3.2.1,<7.0.0
 tooz==2.8.0
 typing-extensions<4.2
-udatetime==0.0.16
 unittest2
 webob==1.8.7
 webtest
diff --git a/st2common/in-requirements.txt b/st2common/in-requirements.txt
index 7dde4932a1..9580fa2fbe 100644
--- a/st2common/in-requirements.txt
+++ b/st2common/in-requirements.txt
@@ -42,7 +42,7 @@ webob
 jsonpath-rw
 pyOpenSSL
 python-statsd
-udatetime
+ciso8601
 orjson
 # Note: amqp is used by kombu, this needs to be added here to be picked up by
 # requirements fixate script.
diff --git a/st2common/requirements.txt b/st2common/requirements.txt
index dc16e87b5f..4757263181 100644
--- a/st2common/requirements.txt
+++ b/st2common/requirements.txt
@@ -10,6 +10,7 @@ amqp==5.0.6
 apscheduler==3.7.0
 cffi<1.15.0
 chardet<3.1.0
+ciso8601
 cryptography==3.4.7
 decorator==4.4.2
 dnspython>=1.16.0,<2.0.0
@@ -43,7 +44,6 @@ six==1.13.0
 st2-rbac-backend@ git+https://github.com/StackStorm/st2-rbac-backend.git@master
 tenacity>=3.2.1,<7.0.0
 tooz==2.8.0
-udatetime==0.0.16
 webob==1.8.7
 zake==0.2.2
 zstandard==0.15.2
diff --git a/st2common/st2common/util/date.py b/st2common/st2common/util/date.py
index 20c5b6e100..ad434bd830 100644
--- a/st2common/st2common/util/date.py
+++ b/st2common/st2common/util/date.py
@@ -21,7 +21,7 @@
 
 import datetime
 
-import udatetime
+import ciso8601
 
 import dateutil.tz
 import dateutil.parser
@@ -83,16 +83,13 @@ def parse(value, preserve_original_tz=False):
 
     :rtype: ``datetime.datetime``
     """
-    # We use udatetime since it's much faster than non-C alternatives
+    # We use ciso8601 since it's much faster than non-C alternatives
     # For compatibility reasons we still fall back to datetutil, but this should rarely happen
     # rfc3339 covers 90% of the iso8601 (it's a subset of it)
     original_value = value
 
     try:
-        if " " in value:
-            # udatetime doesn't support notation with whitespace so we replace it with T
-            value = value.replace(" ", "T")
-        dt = udatetime.from_string(str(value))
+        dt = ciso8601.parse_datetime(str(value))
     except Exception:
         dt = dateutil.parser.parse(str(original_value))