diff --git a/chart-realtime/src/commonMain/kotlin/dev/dtrentin/chart/render/AxisRenderer.kt b/chart-realtime/src/commonMain/kotlin/dev/dtrentin/chart/render/AxisRenderer.kt
index 383e909..a929ac2 100644
--- a/chart-realtime/src/commonMain/kotlin/dev/dtrentin/chart/render/AxisRenderer.kt
+++ b/chart-realtime/src/commonMain/kotlin/dev/dtrentin/chart/render/AxisRenderer.kt
@@ -152,12 +152,14 @@ internal object AxisRenderer {
         }
 
     private fun formatTimeSec(totalSec: Double): String {
-        val s = totalSec.toLong().coerceAtLeast(0L)
-        return when {
+        val negative = totalSec < 0
+        val s = kotlin.math.abs(totalSec.toLong())
+        val formatted = when {
             s < 60L -> "${s}s"
             s < 3600L -> "${s / 60}:${(s % 60).toString().padStart(2, '0')}"
             else -> "${s / 3600}:${((s % 3600) / 60).toString().padStart(2, '0')}:${(s % 60).toString().padStart(2, '0')}"
         }
+        return if (negative) "-$formatted" else formatted
     }
 
     private fun formatAxisValue(value: Double, decimals: Int): String {