First iteration that seems to work

zephcore/adapters/clock/ZephyrRTCClock.cpp

@@ -0,0 +1,22 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "ZephyrRTCClock.h"
+#include <zephyr/kernel.h>
+
+namespace mesh {
+
+uint32_t ZephyrRTCClock::getCurrentTime()
+{
+	uint32_t uptime_sec = (uint32_t)(k_uptime_get() / 1000);
+	return epoch_offset + uptime_sec;
+}
+
+void ZephyrRTCClock::setCurrentTime(uint32_t time)
+{
+	uint32_t uptime_sec = (uint32_t)(k_uptime_get() / 1000);
+	epoch_offset = time - uptime_sec;
+}
+
+} /* namespace mesh */