diff --git a/monitor_turtles.lua b/monitor_turtles.lua
index fa19a70..0b0dc67 100644
--- a/monitor_turtles.lua
+++ b/monitor_turtles.lua
@@ -35,9 +35,9 @@ local function draw()
 
     table.insert(output, "Turtle Monitor")
     for id, data in pairs(turtleStates) do
-        local age = os.clock() - data.time
+        local age = os.time() - data.time
         local status = (age > 10) and "offline" or data.status
-        local line = string.format("%s (ID %d): %s - %s - %s", data.label, id, status, os.clock(), data.time)
+        local line = string.format("%s (ID %d): %s - %s - %s", data.label, id, status, os.time(), data.time)
         table.insert(output, line)
     end