diff --git a/ArduCopter/mode_auto.cpp b/ArduCopter/mode_auto.cpp
index c33c9d98d7ecb..1c0a1880592c1 100644
--- a/ArduCopter/mode_auto.cpp
+++ b/ArduCopter/mode_auto.cpp
@@ -2077,7 +2077,7 @@ bool ModeAuto::verify_loiter_time(const AP_Mission::Mission_Command& cmd)
     }
 
     // start our loiter timer
-    if ( loiter_time == 0 ) {
+    if ( loiter_time == 0_ms ) {
         loiter_time = millis();
     }
 
@@ -2152,7 +2152,7 @@ bool ModeAuto::verify_nav_wp(const AP_Mission::Mission_Command& cmd)
     }
 
     // start timer if necessary
-    if (loiter_time == 0) {
+    if (loiter_time == 0_ms) {
         loiter_time = millis();
         if (loiter_time_max > 0) {
             // play a tone
@@ -2227,7 +2227,7 @@ bool ModeAuto::verify_nav_guided_enable(const AP_Mission::Mission_Command& cmd)
 bool ModeAuto::verify_nav_delay(const AP_Mission::Mission_Command& cmd)
 {
     if (millis() - nav_delay_time_start_ms > nav_delay_time_max_ms) {
-        nav_delay_time_max_ms = 0;
+        nav_delay_time_max_ms = 0_ms;
         return true;
     }
     return false;
diff --git a/ArduCopter/mode_flowhold.cpp b/ArduCopter/mode_flowhold.cpp
index 91814ab45f346..e0b73009f1a9e 100644
--- a/ArduCopter/mode_flowhold.cpp
+++ b/ArduCopter/mode_flowhold.cpp
@@ -318,7 +318,7 @@ void ModeFlowHold::run()
     get_pilot_desired_lean_angles(bf_angles.x, bf_angles.y, angle_max, attitude_control->get_althold_lean_angle_max_cd());
 
     if (quality_filtered >= flow_min_quality &&
-        AP_HAL::millis() - copter.arm_time_ms > 3000) {
+        AP_HAL::millis() - copter.arm_time_ms > 3_s) {
         // don't use for first 3s when we are just taking off
         Vector2f flow_angles;
 
@@ -353,7 +353,7 @@ void ModeFlowHold::update_height_estimate(void)
     // assume on ground when disarmed, or if we have only just started spooling the motors up
     if (!hal.util->get_soft_armed() ||
         copter.motors->get_desired_spool_state() != AP_Motors::DesiredSpoolState::THROTTLE_UNLIMITED ||
-        AP_HAL::millis() - copter.arm_time_ms < 1500) {
+        AP_HAL::millis() - copter.arm_time_ms < 1500_ms) {
         height_offset = -ins_height;
         last_ins_height = ins_height;
         return;
diff --git a/ArduCopter/mode_follow.cpp b/ArduCopter/mode_follow.cpp
index a0649c5956c24..938cbea8329e8 100644
--- a/ArduCopter/mode_follow.cpp
+++ b/ArduCopter/mode_follow.cpp
@@ -152,7 +152,7 @@ void ModeFollow::run()
     // log output at 10hz
     uint32_t now = AP_HAL::millis();
     bool log_request = false;
-    if ((now - last_log_ms >= 100) || (last_log_ms == 0)) {
+    if ((now - last_log_ms >= 100_ms) || (last_log_ms == 0_ms)) {
         log_request = true;
         last_log_ms = now;
     }
diff --git a/ArduCopter/mode_guided.cpp b/ArduCopter/mode_guided.cpp
index 9c2914de8b7bf..9f2c7d159fc99 100644
--- a/ArduCopter/mode_guided.cpp
+++ b/ArduCopter/mode_guided.cpp
@@ -1034,7 +1034,7 @@ void ModeGuided::limit_init_time_and_pos()
 bool ModeGuided::limit_check()
 {
     // check if we have passed the timeout
-    if ((guided_limit.timeout_ms > 0) && (millis() - guided_limit.start_time >= guided_limit.timeout_ms)) {
+    if ((guided_limit.timeout_ms > 0_ms) && (millis() - guided_limit.start_time >= guided_limit.timeout_ms)) {
         return true;
     }
 
diff --git a/ArduCopter/mode_smart_rtl.cpp b/ArduCopter/mode_smart_rtl.cpp
index dacd7cc5f29ab..eed6d1f2c1843 100644
--- a/ArduCopter/mode_smart_rtl.cpp
+++ b/ArduCopter/mode_smart_rtl.cpp
@@ -118,7 +118,7 @@ void ModeSmartRTL::path_follow_run()
         } else if (path_follow_last_pop_fail_ms == 0) {
             // first time we've failed to pop off (ever, or after a success)
             path_follow_last_pop_fail_ms = AP_HAL::millis();
-        } else if (AP_HAL::millis() - path_follow_last_pop_fail_ms > 10000) {
+        } else if (AP_HAL::millis() - path_follow_last_pop_fail_ms > 10_s) {
             // we failed to pop a point off for 10 seconds.  This is
             // almost certainly a bug.
             INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
diff --git a/ArduCopter/mode_throw.cpp b/ArduCopter/mode_throw.cpp
index c9ff702e3fd88..c97daff6a8e82 100644
--- a/ArduCopter/mode_throw.cpp
+++ b/ArduCopter/mode_throw.cpp
@@ -202,7 +202,7 @@ void ModeThrow::run()
 
     // log at 10hz or if stage changes
     uint32_t now = AP_HAL::millis();
-    if ((stage != prev_stage) || (now - last_log_ms) > 100) {
+    if ((stage != prev_stage) || (now - last_log_ms) > 100_ms) {
         prev_stage = stage;
         last_log_ms = now;
         const float velocity = inertial_nav.get_velocity_neu_cms().length();
@@ -276,13 +276,13 @@ bool ModeThrow::throw_detected()
     bool possible_throw_detected = (free_falling || high_speed) && changing_height && no_throw_action;
 
     // Record time and vertical velocity when we detect the possible throw
-    if (possible_throw_detected && ((AP_HAL::millis() - free_fall_start_ms) > 500)) {
+    if (possible_throw_detected && ((AP_HAL::millis() - free_fall_start_ms) > 500_ms)) {
         free_fall_start_ms = AP_HAL::millis();
         free_fall_start_velz = inertial_nav.get_velocity_z_up_cms();
     }
 
     // Once a possible throw condition has been detected, we check for 2.5 m/s of downwards velocity change in less than 0.5 seconds to confirm
-    bool throw_condition_confirmed = ((AP_HAL::millis() - free_fall_start_ms < 500) && ((inertial_nav.get_velocity_z_up_cms() - free_fall_start_velz) < -250.0f));
+    bool throw_condition_confirmed = ((AP_HAL::millis() - free_fall_start_ms < 500_ms) && ((inertial_nav.get_velocity_z_up_cms() - free_fall_start_velz) < -250.0f));
 
     // start motors and enter the control mode if we are in continuous freefall
     return throw_condition_confirmed;
diff --git a/ArduCopter/mode_turtle.cpp b/ArduCopter/mode_turtle.cpp
index 74dc49421ecff..27dc647979eb4 100644
--- a/ArduCopter/mode_turtle.cpp
+++ b/ArduCopter/mode_turtle.cpp
@@ -172,7 +172,7 @@ void ModeTurtle::output_to_motors()
     // throttle needs to be raised
     if (is_zero(channel_throttle->norm_input_dz())) {
         const uint32_t now = AP_HAL::millis();
-        if (now - last_throttle_warning_output_ms > 5000) {
+        if (now - last_throttle_warning_output_ms > 5_s) {
             gcs().send_text(MAV_SEVERITY_WARNING, "Turtle: raise throttle to arm");
             last_throttle_warning_output_ms = now;
         }
diff --git a/ArduCopter/mode_zigzag.cpp b/ArduCopter/mode_zigzag.cpp
index 2952158ec615a..71284388cda1c 100644
--- a/ArduCopter/mode_zigzag.cpp
+++ b/ArduCopter/mode_zigzag.cpp
@@ -404,7 +404,7 @@ bool ModeZigZag::reached_destination()
 
     // wait at time which is set in zigzag_wp_delay
     uint32_t now = AP_HAL::millis();
-    if (reach_wp_time_ms == 0) {
+    if (reach_wp_time_ms == 0_ms) {
         reach_wp_time_ms = now;
     }
     return ((now - reach_wp_time_ms) >= (uint16_t)constrain_int16(_wp_delay, 0, 127) * 1000);