diff --git a/src/protocol.c b/src/protocol.c
index 64a7ae2..d89603d 100644
--- a/src/protocol.c
+++ b/src/protocol.c
@@ -12,3 +12,35 @@
 
 	return 0;
 }
+
+#include <sys/time.h>
+#include <osmocom/gsm/gsm_utils.h>
+
+uint32_t diag_ts_to_fn(uint64_t ts)
+{
+	return (ts/204800)%GSM_MAX_FN;
+}
+
+uint32_t diag_ts_to_epoch(uint64_t qd_time)
+{
+	double qd_ts;
+
+	qd_ts = osmo_load64le(&qd_time);
+	qd_ts *= 1.25*256.0/1000.0;
+
+	/* Sanity check on timestamp (year > 2011) */
+	if (qd_ts < 1000000000) {
+		/* Use current time */
+		int rv = -1;
+		struct timeval tv;
+
+		rv = gettimeofday(&tv, NULL);
+		if (0 == rv)
+			return tv.tv_sec;
+	} else {
+		/* Adjust timestamp from GPS to UNIX */
+		qd_ts += 315964800.0;
+	}
+
+	return qd_ts;
+}