diff --git a/reactor-plc/plc.lua b/reactor-plc/plc.lua
index 6e92cfd..67708d5 100644
--- a/reactor-plc/plc.lua
+++ b/reactor-plc/plc.lua
@@ -1,5 +1,6 @@
 -- #REQUIRES comms.lua
 -- #REQUIRES ppm.lua
+-- #REQUIRES util.lua
 
 local PROTOCOLS = comms.PROTOCOLS
 local RPLC_TYPES = comms.RPLC_TYPES
@@ -272,7 +273,7 @@ function comms_init(id, modem, local_port, server_port, reactor, iss)
 
     -- keep alive ack
     local _send_keep_alive_ack = function (srv_time)
-        _send(RPLC_TYPES.KEEP_ALIVE, { srv_time, os.epoch() })
+        _send(RPLC_TYPES.KEEP_ALIVE, { srv_time, util.time() })
     end
 
     -- general ack
@@ -369,7 +370,7 @@ function comms_init(id, modem, local_port, server_port, reactor, iss)
                     if packet.type == RPLC_TYPES.KEEP_ALIVE then
                         -- keep alive request received, echo back
                         local timestamp = packet.data[1]
-                        local trip_time = os.epoch() - timestamp
+                        local trip_time = util.time() - timestamp
 
                         if trip_time < 0 then
                             log._warning("PLC KEEP_ALIVE trip time less than 0 (" .. trip_time .. ")") 
@@ -494,7 +495,7 @@ function comms_init(id, modem, local_port, server_port, reactor, iss)
         end
 
         local sys_status = {
-            os.epoch(),
+            util.time(),
             (not self.scrammed),
             overridden,
             degraded,
diff --git a/scada-common/alarm.lua b/scada-common/alarm.lua
index d6670a4..e8464a5 100644
--- a/scada-common/alarm.lua
+++ b/scada-common/alarm.lua
@@ -1,3 +1,5 @@
+-- #REQUIRES util.lua
+
 SEVERITY = {
     INFO = 0,       -- basic info message
     WARNING = 1,    -- warning about some abnormal state
@@ -9,7 +11,7 @@ SEVERITY = {
 
 function scada_alarm(severity, device, message)
     local self = {
-        time = os.epoch(),
+        time = util.time(),
         ts_string = os.date("[%H:%M:%S]"),
         severity = severity,
         device = device,
diff --git a/scada-common/util.lua b/scada-common/util.lua
index 1d4e11c..050b18a 100644
--- a/scada-common/util.lua
+++ b/scada-common/util.lua
@@ -1,3 +1,5 @@
+-- PRINT --
+
 -- we are overwriting 'print' so save it first
 local _print = print
 
@@ -21,6 +23,28 @@ function println_ts(message)
     _print(os.date("[%H:%M:%S] ") .. message)
 end
 
+-- TIME --
+
+function time_ms()
+    return os.epoch('local')
+end
+
+function time_s()
+    return os.epoch('local') / 1000
+end
+
+function time()
+    return time_ms()
+end
+
+-- PARALLELIZATION --
+
+-- block waiting for parallel call
+function task_wait(f)
+    parallel.waitForAll(f)
+end
+
+-- WATCHDOG --
 
 -- ComputerCraft OS Timer based Watchdog
 -- triggers a timer event if not fed within 'timeout' seconds
diff --git a/supervisor/session/plc.lua b/supervisor/session/plc.lua
index 3adb85d..695b34b 100644
--- a/supervisor/session/plc.lua
+++ b/supervisor/session/plc.lua
@@ -185,7 +185,7 @@ function new_session(id, for_reactor, in_queue, out_queue)
                 if rplc_pkt.length == 2 then
                     local srv_start = rplc_pkt.data[1]
                     local plc_send = rplc_pkt.data[2]
-                    local srv_now = os.epoch()
+                    local srv_now = util.time()
                     self.last_rtt = srv_now - srv_start
 
                     if self.last_rtt < 0 then
@@ -351,7 +351,7 @@ function new_session(id, for_reactor, in_queue, out_queue)
             self.periodics.keep_alive = self.periodics.keep_alive + elapsed
 
             if self.periodics.keep_alive >= PERIODICS.KEEP_ALIVE then
-                _send(RPLC_TYPES.KEEP_ALIVE, { os.epoch() })
+                _send(RPLC_TYPES.KEEP_ALIVE, { util.time() })
                 self.periodics.keep_alive = 0
             end