diff --git a/themes/command_duration.theme.bash b/themes/command_duration.theme.bash
index c0772d2d..791c8d49 100644
--- a/themes/command_duration.theme.bash
+++ b/themes/command_duration.theme.bash
@@ -1,21 +1,13 @@
 # shellcheck shell=bash
+#
+# Functions for measuring and reporting how long a command takes to run.
 
-if [[ "${BASH_IT_COMMAND_DURATION:-false}" != true ]]; then
-	_command_duration() {
-		echo -n
-	}
-	return
-fi
+: "${COMMAND_DURATION_START_SECONDS:=${EPOCHREALTIME:-$SECONDS}}"
+: "${COMMAND_DURATION_ICON:=🕘}"
+: "${COMMAND_DURATION_MIN_SECONDS:=1}"
 
-COMMAND_DURATION_START_TIME=
-
-COMMAND_DURATION_ICON=${COMMAND_DURATION_ICON:-'  '} 🕘
-COMMAND_DURATION_MIN_SECONDS=${COMMAND_DURATION_MIN_SECONDS:-'1'}
-
-_command_duration_pre_exec() {
-	local command_nano_now="$(date +%1N)"
-	[[ "$command_nano_now" == "1N" ]] && command_nano_now=1
-	COMMAND_DURATION_START_TIME="$(date "+%s").${command_nano_now}"
+function _command_duration_pre_exec() {
+	COMMAND_DURATION_START_SECONDS="${EPOCHREALTIME:-$SECONDS}"
 }
 
 function _dynamic_clock_icon {
@@ -23,43 +15,37 @@ function _dynamic_clock_icon {
 	printf -v 'COMMAND_DURATION_ICON' '%b' "\xf0\x9f\x95\x$clock_hand"
 }
 
-_command_duration() {
-	local command_duration command_start current_time
-	local minutes seconds deciseconds
-	local command_start_sseconds current_time_seconds command_start_deciseconds current_time_deciseconds
-	local command_nano_now="$(date +%1N)"
-	[[ "$command_nano_now" == "1N" ]] && command_nano_now=1
-	current_time="$(date "+%s").${command_nano_now}"
+function _command_duration() {
+	[[ -n "${BASH_IT_COMMAND_DURATION:-}" ]] || return
 
-	if [[ -n "${COMMAND_DURATION_START_TIME:-}" ]]; then
-		_bash_it_log_section="command_duration" _log_debug "calculating start time"
-		command_start_sseconds=${COMMAND_DURATION_START_TIME%.*}
-		current_time_seconds=${current_time%.*}
-
-		command_start_deciseconds=$((10#${command_start#*.}))
-		current_time_deciseconds=$((10#${current_time#*.}))
+	local command_duration=0 command_start="${COMMAND_DURATION_START_SECONDS:-0}"
+	local -i minutes=0 seconds=0 deciseconds=0
+	local -i command_start_seconds="${command_start%.*}"
+	local -i command_start_deciseconds=$((10#${command_start##*.}))
+	local current_time="${EPOCHREALTIME:-$SECONDS}"
+	local -i current_time_seconds="${current_time%.*}"
+	local -i current_time_deciseconds="$((10#${current_time##*.}))"
 
+	if [[ "${command_start_seconds:-0}" -gt 0 ]]; then
 		# seconds
-		command_duration=$((current_time_seconds - command_start_sseconds))
-		_bash_it_log_section="command_duration" _log_debug "duration: $command_duration (from $COMMAND_DURATION_START_TIME to $current_time)"
+		command_duration="$((current_time_seconds - command_start_seconds))"
 
 		if ((current_time_deciseconds >= command_start_deciseconds)); then
-			deciseconds=$(((current_time_deciseconds - command_start_deciseconds)))
+			deciseconds="$((current_time_deciseconds - command_start_deciseconds))"
 		else
 			((command_duration -= 1))
-			deciseconds=$((10 - ((command_start_deciseconds - current_time_deciseconds))))
+			deciseconds="$((10 - (command_start_deciseconds - current_time_deciseconds)))"
 		fi
 	else
 		command_duration=0
 	fi
 
 	if ((command_duration > 0)); then
-		_bash_it_log_section="command_duration" _log_debug "calculating minutes and seconds"
 		minutes=$((command_duration / 60))
 		seconds=$((command_duration % 60))
 	fi
 
-	_dynamic_clock_icon
+	_dynamic_clock_icon "${command_duration}"
 	if ((minutes > 0)); then
 		printf "%s%s%dm %ds" "${COMMAND_DURATION_ICON:-}" "${COMMAND_DURATION_COLOR:-}" "$minutes" "$seconds"
 	elif ((seconds >= COMMAND_DURATION_MIN_SECONDS)); then
@@ -67,4 +53,4 @@ _command_duration() {
 	fi
 }
 
-preexec_functions+=(_command_duration_pre_exec)
+safe_append_preexec '_command_duration_pre_exec'