diff --git a/CHANGELOG.md b/CHANGELOG.md
index c690e34d..ec1edfca 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 * Improve: add workaround to remove empty lines in item to avoid reject by vobject parser
 * Improve: check/enforce RECURRENCE-ID MUST have the same value type as DTSTART in the recurring component (RFC 5545 3.8.4.4)
 * Fix: RECURRENCE-ID comparison on all-day events
+* Fix: format_ut problem on 32-bit systems (got lost inbetween since fixed in 3.5.8)
 
 ## 3.6.0
 
diff --git a/radicale/utils.py b/radicale/utils.py
index 54b80913..8d7ba914 100644
--- a/radicale/utils.py
+++ b/radicale/utils.py
@@ -338,10 +338,13 @@ def format_ut(unixtime: int) -> str:
     elif unixtime >= DATETIME_MAX_UNIXTIME:
         r = str(unixtime) + "(>=MAX:" + str(DATETIME_MAX_UNIXTIME) + ")"
     else:
-        if sys.version_info < (3, 11):
-            dt = datetime.datetime.utcfromtimestamp(unixtime)
+        if sys.maxsize > 2**32:
+            if sys.version_info < (3, 11):
+                dt = datetime.datetime.utcfromtimestamp(unixtime)
+            else:
+                dt = datetime.datetime.fromtimestamp(unixtime, datetime.UTC)
         else:
-            dt = datetime.datetime.fromtimestamp(unixtime, datetime.UTC)
+            dt = datetime.datetime(1970, 1, 1, tzinfo=datetime.timezone.utc) + datetime.timedelta(seconds=unixtime)
         r = str(unixtime) + "(" + dt.strftime('%Y-%m-%dT%H:%M:%SZ') + ")"
     return r