diff --git a/bento_lib/events/_event_bus.py b/bento_lib/events/_event_bus.py
index 9aef2a7..262cf5d 100644
--- a/bento_lib/events/_event_bus.py
+++ b/bento_lib/events/_event_bus.py
@@ -127,7 +127,10 @@ def _make_event(event_type: str, event_data, attrs: dict) -> str:
         return json.dumps({
             # Generate a random ID, so other services can decide how to claim specific events or whatever:
             "id": str(uuid.uuid4()),
-            # Events can arrive out-of-order; we can put them back in order using this generation-time timestamp:
+            # Events can arrive out-of-order; we can put them back in order using this generation-time timestamp
+            # (UTC timezone, in milliseconds):
+            "timestamp": round(datetime.now(timezone.utc).timestamp() * 1000),
+            # legacy version: "ts"  TODO: deprecated: remove
             "ts": datetime.now(timezone.utc).isoformat(),
             "type": event_type.lower(),
             "data": event_data,
diff --git a/bento_lib/package.cfg b/bento_lib/package.cfg
index 9cc1286..6a8748e 100644
--- a/bento_lib/package.cfg
+++ b/bento_lib/package.cfg
@@ -1,5 +1,5 @@
 [package]
 name = bento_lib
-version = 11.2.0
+version = 11.3.0
 authors = David Lougheed, Paul Pillot
 author_emails = david.lougheed@mail.mcgill.ca, paul.pillot@computationalgenomics.ca
diff --git a/tests/test_events.py b/tests/test_events.py
index 7185c65..129ea3d 100644
--- a/tests/test_events.py
+++ b/tests/test_events.py
@@ -64,6 +64,7 @@ def handle_service_event(message):
             assert event["data"] == TEST_EVENT_BODY
             assert event["id"]
             assert event["ts"]
+            assert isinstance(event["timestamp"], int)
 
         event_bus.add_handler(bento_lib.events.ALL_SERVICE_EVENTS, handle_service_event)
         event_bus.start_event_loop()