diff --git a/ESP32/FvHNTP/FvHNTP.cpp b/ESP32/FvHNTP/FvHNTP.cpp
index a8e4e1d..2982149 100644
--- a/ESP32/FvHNTP/FvHNTP.cpp
+++ b/ESP32/FvHNTP/FvHNTP.cpp
@@ -32,6 +32,25 @@ struct sntp_datagram
         uint32_t transmit_timestamp_fraq;
 };
 
+uint64_t get_us_from_ntp(const uint32_t high, const uint32_t low)
+{
+	return uint64_t(ntohl(high)) * 1000000ll + ntohl(low) / 4295;
+}
+
+uint64_t micros64()
+{
+	static uint32_t low32 = 0, high32 = 0;
+
+	uint32_t new_low32 = micros();
+
+	if (new_low32 < low32)
+		high32++;
+
+	low32 = new_low32;
+
+	return (uint64_t(high32) << 32) | low32;
+}
+
 ntp::ntp(const std::string & server): server(server)
 {
 }
@@ -51,21 +70,16 @@ void ntp::begin()
 	th = new std::thread(std::ref(*this));
 }
 
-std::optional<uint64_t> ntp::get_unix_epoch_ms()
+std::optional<uint64_t> ntp::get_unix_epoch_us()
 {
 	std::unique_lock<std::mutex> lck(lock);
 
 	if (ntp_at_ts == 0)
 		return { };
 
-	auto now = millis();
+	auto now = micros64();
 
-	return ntp_at_ts + now - millis_at_ts - NTP_EPOCH * 1000;
-}
-
-uint64_t get_ms_from_ntp(const uint32_t high, const uint32_t low)
-{
-	return uint64_t(ntohl(high)) * 1000ll + ntohl(low) / (4295 * 1000);
+	return ntp_at_ts + now - micros_at_ts - NTP_EPOCH * 1000000l;
 }
 
 void ntp::operator()()
@@ -87,11 +101,11 @@ void ntp::operator()()
 		packet_out.stratum = 14;
 		packet_out.poll    = 2;
 
-		auto now = get_unix_epoch_ms();
+		auto now = get_unix_epoch_us();
 
 		if (now.has_value()) {
-			uint64_t sec  = now.value() / 1000;
-			uint64_t usec = (now.value() % 1000) * 1000;
+			uint64_t sec  = now.value() / 1000000l;
+			uint64_t usec = now.value() % 1000000l;
 
 			packet_out.originate_timestamp_secs = htonl(sec + NTP_EPOCH);  // T1
 			packet_out.originate_timestamp_fraq = htonl(usec * 4295);
@@ -103,37 +117,36 @@ void ntp::operator()()
 			// TODO verify source address
 			if (recvfrom(fd, &packet_in, sizeof(packet_in), 0, nullptr, nullptr) == sizeof(packet_in)) {
 				// TODO verify version etc
-				uint32_t now  = millis();
-				auto     t_t4 = get_unix_epoch_ms();
+				uint64_t now  = micros64();
+				auto     t_t4 = get_unix_epoch_us();
 
 				std::unique_lock<std::mutex> lck(lock);
 
 				s = 60;
 
 				if (t_t4.has_value()) {
-					int64_t t1     = get_ms_from_ntp(packet_out.originate_timestamp_secs, packet_out.originate_timestamp_fraq);
-					int64_t t2     = get_ms_from_ntp(packet_in.receive_timestamp_seqs,    packet_in.receive_timestamp_fraq   );
-					int64_t t3     = get_ms_from_ntp(packet_in.transmit_timestamp_secs,   packet_in.transmit_timestamp_fraq  );
-					int64_t t4     = t_t4.value() + NTP_EPOCH * 1000;
+					int64_t t1     = get_us_from_ntp(packet_out.originate_timestamp_secs, packet_out.originate_timestamp_fraq);
+					int64_t t2     = get_us_from_ntp(packet_in.receive_timestamp_seqs,    packet_in.receive_timestamp_fraq   );
+					int64_t t3     = get_us_from_ntp(packet_in.transmit_timestamp_secs,   packet_in.transmit_timestamp_fraq  );
+					int64_t t4     = t_t4.value() + NTP_EPOCH * 1000000l;
 
 					auto    offset = ((t2 - t1) + (t3 - t4)) / 2;
 
-					// TODO handle millis wrap
 					if (offset > 0) {
-						if (offset < millis_at_ts)
-							millis_at_ts -= offset;
+						if (offset < micros_at_ts)
+							micros_at_ts -= offset;
 						else {
-							millis_at_ts = 0;
+							micros_at_ts = 0;
 							s            = 4;
 						}
 					}
 					else {
-						millis_at_ts -= offset;
+						micros_at_ts -= offset;
 					}
 				}
 				else {
-					ntp_at_ts    = get_ms_from_ntp(packet_in.transmit_timestamp_secs, packet_in.transmit_timestamp_fraq);
-					millis_at_ts = now;
+					ntp_at_ts    = get_us_from_ntp(packet_in.transmit_timestamp_secs, packet_in.transmit_timestamp_fraq);
+					micros_at_ts = now;
 				}
 			}
 		}