diff --git a/oslo_utils/timeutils.py b/oslo_utils/timeutils.py
index 94975c4b..94b728da 100644
--- a/oslo_utils/timeutils.py
+++ b/oslo_utils/timeutils.py
@@ -21,6 +21,7 @@ import calendar
 import datetime
 import time
 
+from debtcollector import removals
 import iso8601
 from pytz import timezone
 import six
@@ -48,8 +49,17 @@ except AttributeError:
         now = time.time
 
 
+@removals.remove(
+    message="use datetime.datetime.isoformat()",
+    version="1.6",
+    removal_version="?",
+    )
 def isotime(at=None, subsecond=False):
-    """Stringify time in ISO 8601 format."""
+    """Stringify time in ISO 8601 format.
+
+    .. deprecated:: > 1.5.0
+       Use :func:`utcnow` and :func:`datetime.datetime.isoformat` instead.
+    """
     if not at:
         at = utcnow()
     st = at.strftime(_ISO8601_TIME_FORMAT
@@ -147,8 +157,18 @@ def utcnow():
     return datetime.datetime.utcnow()
 
 
+@removals.remove(
+    message="use datetime.datetime.utcfromtimestamp().isoformat()",
+    version="1.6",
+    removal_version="?",
+    )
 def iso8601_from_timestamp(timestamp, microsecond=False):
-    """Returns an iso8601 formatted date from timestamp."""
+    """Returns an iso8601 formatted date from timestamp.
+
+    .. deprecated:: > 1.5.0
+       Use :func:`datetime.datetime.utcfromtimestamp` and
+       :func:`datetime.datetime.isoformat` instead.
+    """
     return isotime(datetime.datetime.utcfromtimestamp(timestamp), microsecond)
 
 
diff --git a/requirements.txt b/requirements.txt
index 5a328bef..a3b3d66e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -14,3 +14,4 @@ iso8601>=0.1.9
 oslo.i18n>=1.5.0  # Apache-2.0
 netaddr>=0.7.12
 netifaces>=0.10.4
+debtcollector>=0.3.0  # Apache-2.0