diff --git a/include/Clock.h b/include/Clock.h
index 87ff289..a8bcba3 100644
--- a/include/Clock.h
+++ b/include/Clock.h
@@ -7,9 +7,13 @@
 #define CLOCK_H
 
 #include "NetworkInterface.h"
+#include "mbed.h"
 #include "sntp.h"
 #include <chrono>
 
+typedef std::chrono::time_point<Kernel::Clock> kernel_timepoint;
+std::chrono::microseconds kernel_to_real_time(kernel_timepoint time);
+
 void clock_setup(void);
 SNTPError clock_sync(NetworkInterface &net);
 
diff --git a/src/Clock.cpp b/src/Clock.cpp
index acc181f..aabc005 100644
--- a/src/Clock.cpp
+++ b/src/Clock.cpp
@@ -8,28 +8,68 @@
 
 using namespace std::chrono;
 
+// The time the system started in microseconds since 1970
+microseconds boot_start;
+// Always use this lock to access boot_start
+Mutex boot_start_access;
+
+// Sets the boot_start time based on kernel uptime and real time
+// in microseconds since 1970
+// This is done by removing the uptime from the real time to get the
+// time the system booted
+// Both kernel_time and real_time should be sampled at the same time
+void set_boot_start(kernel_timepoint kernel_time, microseconds real_time) {
+	microseconds uptime = kernel_time.time_since_epoch();
+	boot_start_access.lock();
+	boot_start = real_time - uptime;
+	boot_start_access.unlock();
+}
+
+// Converts a kernel timepoint to microseconds since 1970
+// This is done by adding boot_start to the kernel time passed
+microseconds kernel_to_real_time(kernel_timepoint kernel_time) {
+	microseconds boot_time = kernel_time.time_since_epoch();
+	boot_start_access.lock();
+	microseconds real_time = boot_start + boot_time;
+	boot_start_access.unlock();
+	return real_time;
+}
+
 // Initializes the clock, run once at boot
 void clock_setup(void) {
-	// mbed reads the RTC at boot, do nothing for now
+	// Get RTC time
+	time_t rtc_time = time(NULL);
+	// Update boot start time
+	microseconds rtc_time_microsecs = seconds(rtc_time);
+	kernel_timepoint kernel_now = Kernel::Clock::now();
+	set_boot_start(kernel_now, rtc_time_microsecs);
 }
 
 // Syncs the clock using SNTP, run any time
 SNTPError clock_sync(NetworkInterface &net) {
+	// Get time from SNTP
 	struct timeval time;
 	SNTPError err;
 	err = sntp(net, "time.google.com", 123, &time);
 	if (err != SNTPSuccess) {
 		return err;
 	}
+	// Set RTC time
 	set_time(time.tv_sec);
+	// Convert SNTP timeval to microseconds
+	microseconds time_microsecs(0);
+	time_microsecs += seconds(time.tv_sec);
+	time_microsecs += microseconds(time.tv_usec);
+	// Update boot start time
+	kernel_timepoint kernel_now = Kernel::Clock::now();
+	set_boot_start(kernel_now, time_microsecs);
 	return SNTPSuccess;
 }
 
 // Gets the current clock time in microseconds since 1970
 microseconds clock_now(void) {
-	time_t now_seconds = time(NULL);
-	microseconds microsecs = seconds(now_seconds);
-	return microsecs;
+	kernel_timepoint kernel_now = Kernel::Clock::now();
+	return kernel_to_real_time(kernel_now);
 }
 
 // Formats a time in microseconds using strftime