diff --git a/firmware/application/app_ais.cpp b/firmware/application/app_ais.cpp
index c18b00f6..89b33ac2 100644
--- a/firmware/application/app_ais.cpp
+++ b/firmware/application/app_ais.cpp
@@ -158,7 +158,7 @@ static std::string format_latlon_normalized(const int32_t normalized) {
 static std::string format_datetime(
 	const DateTime& datetime
 ) {
-	return ui::to_string_dec_uint(datetime.year, 4) + "/" +
+	return ui::to_string_dec_uint(datetime.year, 4, '0') + "/" +
 		ui::to_string_dec_uint(datetime.month, 2, '0') + "/" +
 		ui::to_string_dec_uint(datetime.day, 2, '0') + " " +
 		ui::to_string_dec_uint(datetime.hour, 2, '0') + ":" +
diff --git a/firmware/application/app_tpms.cpp b/firmware/application/app_tpms.cpp
index 67da089d..d159cecf 100644
--- a/firmware/application/app_tpms.cpp
+++ b/firmware/application/app_tpms.cpp
@@ -50,7 +50,7 @@ ManchesterFormatted TPMSModel::on_packet(const TPMSPacketMessage& message) {
 		rtc::RTC datetime;
 		rtcGetTime(&RTCD1, &datetime);
 		std::string timestamp = 
-			ui::to_string_dec_uint(datetime.year(), 4) +
+			ui::to_string_dec_uint(datetime.year(), 4, '0') +
 			ui::to_string_dec_uint(datetime.month(), 2, '0') +
 			ui::to_string_dec_uint(datetime.day(), 2, '0') +
 			ui::to_string_dec_uint(datetime.hour(), 2, '0') +