diff --git a/gen/flights/flightplan.py b/gen/flights/flightplan.py
index bbc954d8..a8cccf9a 100644
--- a/gen/flights/flightplan.py
+++ b/gen/flights/flightplan.py
@@ -7,6 +7,7 @@ generating the waypoints for the mission.
 """
 from __future__ import annotations
 
+import math
 from datetime import timedelta
 from functools import cached_property
 import logging
@@ -93,29 +94,31 @@ class PackageWaypointTiming:
         if group_ground_speed is None:
             return None
 
-        ingress = package.time_over_target - TravelTime.between_points(
-            package.waypoints.ingress,
-            package.target.position,
-            group_ground_speed
-        )
+        # Round each waypoint TOT since DCS doesn't support sub-second timing
+        # and it's not interesting to the user.
+        ingress = timedelta(seconds=math.floor(
+            (package.time_over_target - TravelTime.between_points(
+                package.waypoints.ingress,
+                package.target.position,
+                group_ground_speed)).total_seconds()))
 
-        join = ingress - TravelTime.between_points(
-            package.waypoints.join,
-            package.waypoints.ingress,
-            group_ground_speed
-        )
+        join = timedelta(seconds=math.floor(
+            (ingress - TravelTime.between_points(
+                package.waypoints.join,
+                package.waypoints.ingress,
+                group_ground_speed)).total_seconds()))
 
-        egress = package.time_over_target + TravelTime.between_points(
-            package.target.position,
-            package.waypoints.egress,
-            group_ground_speed
-        )
+        egress = timedelta(seconds=math.floor(
+            (package.time_over_target + TravelTime.between_points(
+                package.target.position,
+                package.waypoints.egress,
+                group_ground_speed)).total_seconds()))
 
-        split = egress + TravelTime.between_points(
-            package.waypoints.egress,
-            package.waypoints.split,
-            group_ground_speed
-        )
+        split = timedelta(seconds=math.floor(
+            (egress + TravelTime.between_points(
+                package.waypoints.egress,
+                package.waypoints.split,
+                group_ground_speed)).total_seconds()))
 
         return cls(package, join, ingress, egress, split)
 
diff --git a/gen/flights/traveltime.py b/gen/flights/traveltime.py
index 644e9851..ee9a6c7e 100644
--- a/gen/flights/traveltime.py
+++ b/gen/flights/traveltime.py
@@ -98,7 +98,17 @@ class TotEstimator:
         takeoff_time = self.takeoff_time_for_flight(flight)
         startup_time = self.estimate_startup(flight)
         ground_ops_time = self.estimate_ground_ops(flight)
-        return takeoff_time - startup_time - ground_ops_time
+        start_time = takeoff_time - startup_time - ground_ops_time
+        # In case FP math has given us some barely below zero time, round to
+        # zero.
+        if math.isclose(start_time.total_seconds(), 0):
+            return timedelta()
+        # Trim microseconds. DCS doesn't handle sub-second resolution for tasks,
+        # and they're not interesting from a mission planning perspective so we
+        # don't want them in the UI.
+        #
+        # Round down so *barely* above zero start times are just zero.
+        return timedelta(seconds=math.floor(start_time.total_seconds()))
 
     def takeoff_time_for_flight(self, flight: Flight) -> timedelta:
         travel_time = self.travel_time_to_rendezvous_or_target(flight)
@@ -122,10 +132,17 @@ class TotEstimator:
         return tot - travel_time - self.HOLD_TIME
 
     def earliest_tot(self) -> timedelta:
-        return max((
+        earliest_tot = max((
             self.earliest_tot_for_flight(f) for f in self.package.flights
         )) + self.HOLD_TIME
 
+        # Trim microseconds. DCS doesn't handle sub-second resolution for tasks,
+        # and they're not interesting from a mission planning perspective so we
+        # don't want them in the UI.
+        #
+        # Round up so we don't get negative start times.
+        return timedelta(seconds=math.ceil(earliest_tot.total_seconds()))
+
     def earliest_tot_for_flight(self, flight: Flight) -> timedelta:
         """Estimate fastest time from mission start to the target position.