diff --git a/src/shearwater_common.c b/src/shearwater_common.c
index 1e2a65b..ca3f237 100644
--- a/src/shearwater_common.c
+++ b/src/shearwater_common.c
@@ -599,6 +599,91 @@ shearwater_common_wdbi (shearwater_common_device_t *device, unsigned int id, con
 	return status;
 }
 
+dc_status_t
+shearwater_common_timesync_local (shearwater_common_device_t *device, const dc_datetime_t *datetime)
+{
+	dc_status_t status = DC_STATUS_SUCCESS;
+	dc_device_t *abstract = (dc_device_t *) device;
+
+	// Convert to local time.
+	dc_datetime_t local = *datetime;
+	local.timezone = DC_TIMEZONE_NONE;
+
+	dc_ticks_t ticks = dc_datetime_mktime (&local);
+	if (ticks == -1) {
+		ERROR (abstract->context, "Invalid date/time value specified.");
+		return DC_STATUS_INVALIDARGS;
+	}
+
+	const unsigned char timestamp[] = {
+		(ticks >> 24) & 0xFF,
+		(ticks >> 16) & 0xFF,
+		(ticks >>  8) & 0xFF,
+		(ticks      ) & 0xFF,
+	};
+
+	status = shearwater_common_wdbi (device, ID_TIME_LOCAL, timestamp, sizeof(timestamp));
+	if (status != DC_STATUS_SUCCESS) {
+		ERROR (abstract->context, "Failed to write the dive computer local time.");
+		return status;
+	}
+
+	return status;
+}
+
+dc_status_t
+shearwater_common_timesync_utc (shearwater_common_device_t *device, const dc_datetime_t *datetime)
+{
+	dc_status_t status = DC_STATUS_SUCCESS;
+	dc_device_t *abstract = (dc_device_t *) device;
+
+	// Convert to UTC time.
+	dc_ticks_t ticks = dc_datetime_mktime (datetime);
+	if (ticks == -1) {
+		ERROR (abstract->context, "Invalid date/time value specified.");
+		return DC_STATUS_INVALIDARGS;
+	}
+
+	const unsigned char timestamp[] = {
+		(ticks >> 24) & 0xFF,
+		(ticks >> 16) & 0xFF,
+		(ticks >>  8) & 0xFF,
+		(ticks      ) & 0xFF,
+	};
+
+	status = shearwater_common_wdbi (device, ID_TIME_UTC, timestamp, sizeof(timestamp));
+	if (status != DC_STATUS_SUCCESS) {
+		ERROR (abstract->context, "Failed to write the dive computer UTC time.");
+		return status;
+	}
+
+	int timezone = datetime->timezone / 60;
+	const unsigned char offset[] = {
+		(timezone >> 24) & 0xFF,
+		(timezone >> 16) & 0xFF,
+		(timezone >>  8) & 0xFF,
+		(timezone      ) & 0xFF,
+	};
+
+	status = shearwater_common_wdbi (device, ID_TIME_OFFSET, offset, sizeof (offset));
+	if (status != DC_STATUS_SUCCESS) {
+		ERROR (abstract->context, "Failed to write the dive computer timezone offset.");
+		return status;
+	}
+
+	// We don't have a way to determine the daylight savings time setting,
+	// but the required offset is already factored into the timezone offset.
+	const unsigned char dst[] = {0, 0, 0, 0};
+
+	status = shearwater_common_wdbi (device, ID_TIME_DST, dst, sizeof (dst));
+	if (status != DC_STATUS_SUCCESS) {
+		ERROR (abstract->context, "Failed to write the dive computer DST setting.");
+		return status;
+	}
+
+	return status;
+}
+
 unsigned int
 shearwater_common_get_model (shearwater_common_device_t *device, unsigned int hardware)
 {
diff --git a/src/shearwater_common.h b/src/shearwater_common.h
index 1c25b75..4c7f186 100644
--- a/src/shearwater_common.h
+++ b/src/shearwater_common.h
@@ -35,6 +35,11 @@ extern "C" {
 #define ID_LOGUPLOAD 0x8021
 #define ID_HARDWARE  0x8050
 
+#define ID_TIME_LOCAL  0x9030
+#define ID_TIME_UTC    0x9031
+#define ID_TIME_OFFSET 0x9032
+#define ID_TIME_DST    0x9033
+
 #define PREDATOR 2
 #define PETREL   3
 #define PETREL2  PETREL
@@ -70,6 +75,12 @@ shearwater_common_rdbi (shearwater_common_device_t *device, unsigned int id, uns
 dc_status_t
 shearwater_common_wdbi (shearwater_common_device_t *device, unsigned int id, const unsigned char data[], unsigned int size);
 
+dc_status_t
+shearwater_common_timesync_local (shearwater_common_device_t *device, const dc_datetime_t *datetime);
+
+dc_status_t
+shearwater_common_timesync_utc (shearwater_common_device_t *device, const dc_datetime_t *datetime);
+
 unsigned int
 shearwater_common_get_model (shearwater_common_device_t *device, unsigned int hardware);
 
diff --git a/src/shearwater_petrel.c b/src/shearwater_petrel.c
index 0d91c03..7ec18ff 100644
--- a/src/shearwater_petrel.c
+++ b/src/shearwater_petrel.c
@@ -46,6 +46,7 @@ typedef struct shearwater_petrel_device_t {
 
 static dc_status_t shearwater_petrel_device_set_fingerprint (dc_device_t *abstract, const unsigned char data[], unsigned int size);
 static dc_status_t shearwater_petrel_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void *userdata);
+static dc_status_t shearwater_petrel_device_timesync (dc_device_t *abstract, const dc_datetime_t *datetime);
 static dc_status_t shearwater_petrel_device_close (dc_device_t *abstract);
 
 static const dc_device_vtable_t shearwater_petrel_device_vtable = {
@@ -56,7 +57,7 @@ static const dc_device_vtable_t shearwater_petrel_device_vtable = {
 	NULL, /* write */
 	NULL, /* dump */
 	shearwater_petrel_device_foreach, /* foreach */
-	NULL, /* timesync */
+	shearwater_petrel_device_timesync,
 	shearwater_petrel_device_close /* close */
 };
 
@@ -350,3 +351,28 @@ shearwater_petrel_device_foreach (dc_device_t *abstract, dc_dive_callback_t call
 
 	return rc;
 }
+
+static dc_status_t
+shearwater_petrel_device_timesync (dc_device_t *abstract, const dc_datetime_t *datetime)
+{
+	dc_status_t status = DC_STATUS_SUCCESS;
+	shearwater_common_device_t *device = (shearwater_common_device_t *) abstract;
+
+	// Read the hardware type.
+	unsigned char rsp_hardware[2] = {0};
+	status = shearwater_common_rdbi (device, ID_HARDWARE, rsp_hardware, sizeof(rsp_hardware));
+	if (status != DC_STATUS_SUCCESS) {
+		ERROR (abstract->context, "Failed to read the hardware type.");
+		return status;
+	}
+
+	// Convert and map to the model number.
+	unsigned int hardware = array_uint16_be (rsp_hardware);
+	unsigned int model = shearwater_common_get_model (device, hardware);
+
+	if (model == TERIC) {
+		return shearwater_common_timesync_utc (device, datetime);
+	} else {
+		return shearwater_common_timesync_local (device, datetime);
+	}
+}
diff --git a/src/shearwater_predator.c b/src/shearwater_predator.c
index d4c97b4..fffd511 100644
--- a/src/shearwater_predator.c
+++ b/src/shearwater_predator.c
@@ -44,6 +44,7 @@ typedef struct shearwater_predator_device_t {
 static dc_status_t shearwater_predator_device_set_fingerprint (dc_device_t *abstract, const unsigned char data[], unsigned int size);
 static dc_status_t shearwater_predator_device_dump (dc_device_t *abstract, dc_buffer_t *buffer);
 static dc_status_t shearwater_predator_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void *userdata);
+static dc_status_t shearwater_predator_device_timesync (dc_device_t *abstract, const dc_datetime_t *datetime);
 
 static const dc_device_vtable_t shearwater_predator_device_vtable = {
 	sizeof(shearwater_predator_device_t),
@@ -53,7 +54,7 @@ static const dc_device_vtable_t shearwater_predator_device_vtable = {
 	NULL, /* write */
 	shearwater_predator_device_dump, /* dump */
 	shearwater_predator_device_foreach, /* foreach */
-	NULL, /* timesync */
+	shearwater_predator_device_timesync,
 	NULL /* close */
 };
 
@@ -357,3 +358,9 @@ shearwater_predator_extract_dives (dc_device_t *abstract, const unsigned char da
 		return shearwater_predator_extract_predator (abstract, data, size, callback, userdata);
 	}
 }
+
+static dc_status_t
+shearwater_predator_device_timesync (dc_device_t *abstract, const dc_datetime_t *datetime)
+{
+	return shearwater_common_timesync_local ((shearwater_common_device_t *) abstract, datetime);
+}