diff --git a/radio/src/cli.cpp b/radio/src/cli.cpp
index 90edc613c..212aad7f8 100644
--- a/radio/src/cli.cpp
+++ b/radio/src/cli.cpp
@@ -388,7 +388,7 @@ int cliSet(const char ** argv)
     struct gtm t;
     int year, month, day, hour, minute, second;
     if (toInt(argv, 2, &year) > 0 && toInt(argv, 3, &month) > 0 && toInt(argv, 4, &day) > 0 && toInt(argv, 5, &hour) > 0 && toInt(argv, 6, &minute) > 0 && toInt(argv, 7, &second) > 0) {
-      t.tm_year = year-1900;
+      t.tm_year = year-TM_YEAR_BASE;
       t.tm_mon = month-1;
       t.tm_mday = day;
       t.tm_hour = hour;
@@ -587,7 +587,7 @@ int cliDisplay(const char ** argv)
   else if (!strcmp(argv[1], "rtc")) {
     struct gtm utm;
     gettime(&utm);
-    serialPrint("rtc = %4d-%02d-%02d %02d:%02d:%02d.%02d0", utm.tm_year+1900, utm.tm_mon+1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec, g_ms100);
+    serialPrint("rtc = %4d-%02d-%02d %02d:%02d:%02d.%02d0", utm.tm_year+TM_YEAR_BASE, utm.tm_mon+1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec, g_ms100);
   }
   else if (!strcmp(argv[1], "volume")) {
     serialPrint("volume = %d", getVolume());
diff --git a/radio/src/debug.cpp b/radio/src/debug.cpp
index ac98ce7cd..da30be14e 100644
--- a/radio/src/debug.cpp
+++ b/radio/src/debug.cpp
@@ -88,7 +88,7 @@ void dumpTraceBuffer()
     struct gtm tp;
     filltm(&traceBuffer[n].time, &tp);
     TRACE_NOCRLF("%02d  ", n);
-    TRACE_NOCRLF("%4d-%02d-%02d,%02d:%02d:%02d.%02d0", tp.tm_year+1900, tp.tm_mon+1, tp.tm_mday, tp.tm_hour, tp.tm_min, tp.tm_sec, traceBuffer[n].time_ms);
+    TRACE_NOCRLF("%4d-%02d-%02d,%02d:%02d:%02d.%02d0", tp.tm_year+TM_YEAR_BASE, tp.tm_mon+1, tp.tm_mday, tp.tm_hour, tp.tm_min, tp.tm_sec, traceBuffer[n].time_ms);
     TRACE("  %03d    0x%08x", traceBuffer[n].event, traceBuffer[n].data);
     if (traceBuffer[n].time == 0 && traceBuffer[n].time_ms == 0) break;
 #if !defined(SIMU)
diff --git a/radio/src/gui/128x64/radio_setup.cpp b/radio/src/gui/128x64/radio_setup.cpp
index ba54eb55e..aba344d10 100644
--- a/radio/src/gui/128x64/radio_setup.cpp
+++ b/radio/src/gui/128x64/radio_setup.cpp
@@ -163,7 +163,7 @@ void menuRadioSetup(event_t event)
           uint8_t rowattr = (menuHorizontalPosition==j ? attr : 0);
           switch (j) {
             case 0:
-              lcdDrawNumber(RADIO_SETUP_DATE_COLUMN, y, t.tm_year+1900, rowattr|RIGHT);
+              lcdDrawNumber(RADIO_SETUP_DATE_COLUMN, y, t.tm_year+TM_YEAR_BASE, rowattr|RIGHT);
               if (rowattr && (s_editMode>0 || p1valdiff)) t.tm_year = checkIncDec(event, t.tm_year, 112, 200, 0);
               break;
             case 1:
@@ -172,7 +172,7 @@ void menuRadioSetup(event_t event)
               break;
             case 2:
             {
-              int16_t year = 1900 + t.tm_year;
+              int16_t year = TM_YEAR_BASE + t.tm_year;
               int8_t dlim = (((((year%4==0) && (year%100!=0)) || (year%400==0)) && (t.tm_mon==1)) ? 1 : 0);
               static const pm_uint8_t dmon[] PROGMEM = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
               dlim += pgm_read_byte(&dmon[t.tm_mon]);
diff --git a/radio/src/gui/212x64/radio_setup.cpp b/radio/src/gui/212x64/radio_setup.cpp
index a964319c5..cdf781db7 100644
--- a/radio/src/gui/212x64/radio_setup.cpp
+++ b/radio/src/gui/212x64/radio_setup.cpp
@@ -137,7 +137,7 @@ void menuRadioSetup(event_t event)
           uint8_t rowattr = (menuHorizontalPosition==j ? attr : 0);
           switch (j) {
             case 0:
-              lcdDrawNumber(RADIO_SETUP_DATE_COLUMN, y, t.tm_year+1900, rowattr|RIGHT);
+              lcdDrawNumber(RADIO_SETUP_DATE_COLUMN, y, t.tm_year+TM_YEAR_BASE, rowattr|RIGHT);
               if (rowattr && s_editMode>0) t.tm_year = checkIncDec(event, t.tm_year, 112, 200, 0);
               break;
             case 1:
@@ -146,7 +146,7 @@ void menuRadioSetup(event_t event)
               break;
             case 2:
             {
-              int16_t year = 1900 + t.tm_year;
+              int16_t year = TM_YEAR_BASE + t.tm_year;
               int8_t dlim = (((((year%4==0) && (year%100!=0)) || (year%400==0)) && (t.tm_mon==1)) ? 1 : 0);
               static const pm_uint8_t dmon[] PROGMEM = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
               dlim += pgm_read_byte(&dmon[t.tm_mon]);
diff --git a/radio/src/gui/480x272/radio_setup.cpp b/radio/src/gui/480x272/radio_setup.cpp
index 1451b3663..5d3d258ed 100644
--- a/radio/src/gui/480x272/radio_setup.cpp
+++ b/radio/src/gui/480x272/radio_setup.cpp
@@ -143,7 +143,7 @@ bool menuRadioSetup(event_t event)
           uint8_t rowattr = (menuHorizontalPosition==j ? attr : 0);
           switch (j) {
             case 0:
-              lcdDrawNumber(RADIO_SETUP_2ND_COLUMN, y, t.tm_year+1900, flags|rowattr);
+              lcdDrawNumber(RADIO_SETUP_2ND_COLUMN, y, t.tm_year+TM_YEAR_BASE, flags|rowattr);
               if (rowattr && s_editMode>0) t.tm_year = checkIncDec(event, t.tm_year, 112, 200, 0);
               lcdDrawText(lcdNextPos+3, y, "-", flags);
               break;
@@ -154,7 +154,7 @@ bool menuRadioSetup(event_t event)
               break;
             case 2:
             {
-              int16_t year = 1900 + t.tm_year;
+              int16_t year = TM_YEAR_BASE + t.tm_year;
               int8_t dlim = (((((year%4==0) && (year%100!=0)) || (year%400==0)) && (t.tm_mon==1)) ? 1 : 0);
               static const pm_uint8_t dmon[] PROGMEM = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
               dlim += pgm_read_byte(&dmon[t.tm_mon]);
diff --git a/radio/src/logs.cpp b/radio/src/logs.cpp
index e30f9b3b7..53fc1d192 100644
--- a/radio/src/logs.cpp
+++ b/radio/src/logs.cpp
@@ -236,7 +236,7 @@ void logsWrite()
           lastRtcTime = g_rtcTime;
           gettime(&utm);
         }
-        f_printf(&g_oLogFile, "%4d-%02d-%02d,%02d:%02d:%02d.%02d0,", utm.tm_year+1900, utm.tm_mon+1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec, g_ms100);
+        f_printf(&g_oLogFile, "%4d-%02d-%02d,%02d:%02d:%02d.%02d0,", utm.tm_year+TM_YEAR_BASE, utm.tm_mon+1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec, g_ms100);
       }
 #else
       f_printf(&g_oLogFile, "%d,", tmr10ms);
diff --git a/radio/src/lua/api_general.cpp b/radio/src/lua/api_general.cpp
index 7c65dc8e1..4fff1df59 100644
--- a/radio/src/lua/api_general.cpp
+++ b/radio/src/lua/api_general.cpp
@@ -141,7 +141,7 @@ static int luaGetDateTime(lua_State * L)
 {
   struct gtm utm;
   gettime(&utm);
-  luaPushDateTime(L, utm.tm_year + 1900, utm.tm_mon + 1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec);
+  luaPushDateTime(L, utm.tm_year + TM_YEAR_BASE, utm.tm_mon + 1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec);
   return 1;
 }
 
diff --git a/radio/src/rtc.cpp b/radio/src/rtc.cpp
index 49135c4e2..baa5fadce 100644
--- a/radio/src/rtc.cpp
+++ b/radio/src/rtc.cpp
@@ -87,7 +87,6 @@ static_assert(TYPE_TWOS_COMPLEMENT(int), "twos complement arithmetic");
    diagnostic on some hosts.  */
 
 #define EPOCH_YEAR 1970
-#define TM_YEAR_BASE 1900
 static_assert(TM_YEAR_BASE % 100 == 0, "base year is not a multiple of 100");
 
 /* Return 1 if YEAR + TM_YEAR_BASE is a leap year.  */
@@ -148,8 +147,8 @@ int __offtime(const gtime_t * t, long int offset, struct gtm * tp)
     days -= ((yg - y) * 365 + LEAPS_THRU_END_OF(yg - 1) - LEAPS_THRU_END_OF(y - 1));
     y = yg;
   }
-  tp->tm_year = y - 1900;
-  if (tp->tm_year != y - 1900) {
+  tp->tm_year = y - TM_YEAR_BASE;
+  if (tp->tm_year != y - TM_YEAR_BASE) {
     /* The year cannot be represented due to overflow.  */
     // __set_errno (EOVERFLOW);
     return 0;
@@ -465,7 +464,7 @@ uint8_t rtcAdjust(uint16_t year, uint8_t mon, uint8_t day, uint8_t hour, uint8_t
 
     // convert given UTC time to local time (to seconds) and compare it with RTC
     struct gtm t;
-    t.tm_year = year - 1900;
+    t.tm_year = year - TM_YEAR_BASE;
     t.tm_mon  = mon - 1;
     t.tm_mday = day;
     t.tm_hour = hour;
diff --git a/radio/src/rtc.h b/radio/src/rtc.h
index efbe8f3fb..01464cb86 100644
--- a/radio/src/rtc.h
+++ b/radio/src/rtc.h
@@ -25,6 +25,7 @@
 
 #define SECS_PER_HOUR   3600ul
 #define SECS_PER_DAY    86400ul
+#define TM_YEAR_BASE    1900
 
 typedef long int gtime_t;
 
diff --git a/radio/src/strhelpers.cpp b/radio/src/strhelpers.cpp
index 8f98ad749..5f7f15c63 100644
--- a/radio/src/strhelpers.cpp
+++ b/radio/src/strhelpers.cpp
@@ -425,7 +425,7 @@ char * strAppendDate(char * str, bool time)
   str[0] = '-';
   struct gtm utm;
   gettime(&utm);
-  div_t qr = div(utm.tm_year+1900, 10);
+  div_t qr = div(utm.tm_year+TM_YEAR_BASE, 10);
   str[4] = '0' + qr.rem;
   qr = div(qr.quot, 10);
   str[3] = '0' + qr.rem;
diff --git a/radio/src/targets/gruvin9x/rtc_driver.cpp b/radio/src/targets/gruvin9x/rtc_driver.cpp
index 3d5eda507..e1d25b2e2 100644
--- a/radio/src/targets/gruvin9x/rtc_driver.cpp
+++ b/radio/src/targets/gruvin9x/rtc_driver.cpp
@@ -254,7 +254,7 @@ void rtcGetTime(struct gtm * utm)
 
   g9x_rtcGetTime(&rtc);
 
-  utm->tm_year = rtc.year - 1900;
+  utm->tm_year = rtc.year - TM_YEAR_BASE;
   utm->tm_mon =  rtc.month - 1;
   utm->tm_mday = rtc.mday;
   utm->tm_hour = rtc.hour;
@@ -268,7 +268,7 @@ void rtcSetTime(const struct gtm * t)
   g_ms100 = 0; // start of next second begins now
 
   RTC rtc;
-  rtc.year = t->tm_year + 1900;
+  rtc.year = t->tm_year + TM_YEAR_BASE;
   rtc.month = t->tm_mon + 1;
   rtc.mday = t->tm_mday;
   rtc.hour = t->tm_hour;
diff --git a/radio/src/targets/simu/simpgmspace.cpp b/radio/src/targets/simu/simpgmspace.cpp
index 2a2b4e3b7..6e64a879c 100644
--- a/radio/src/targets/simu/simpgmspace.cpp
+++ b/radio/src/targets/simu/simpgmspace.cpp
@@ -1203,7 +1203,7 @@ void RTC_GetDate(uint32_t RTC_Format, RTC_DateTypeDef * RTC_DateStruct)
   time_t tme;
   time(&tme);
   struct tm * timeinfo = localtime(&tme);
-  RTC_DateStruct->RTC_Year = timeinfo->tm_year - 1900;
+  RTC_DateStruct->RTC_Year = timeinfo->tm_year - TM_YEAR_BASE;
   RTC_DateStruct->RTC_Month = timeinfo->tm_mon + 1;
   RTC_DateStruct->RTC_Date = timeinfo->tm_mday;
 }
diff --git a/radio/src/targets/sky9x/coproc_driver.cpp b/radio/src/targets/sky9x/coproc_driver.cpp
index e6dc9a40d..d94106cdc 100644
--- a/radio/src/targets/sky9x/coproc_driver.cpp
+++ b/radio/src/targets/sky9x/coproc_driver.cpp
@@ -164,7 +164,7 @@ extern "C" void TWI0_IRQHandler()
         utm.tm_hour = Co_proc_status[3] ;
         utm.tm_mday = Co_proc_status[4] ;
         utm.tm_mon = Co_proc_status[5] - 1;
-        utm.tm_year = (Co_proc_status[6] + ( Co_proc_status[7] << 8 )) - 1900;
+        utm.tm_year = (Co_proc_status[6] + ( Co_proc_status[7] << 8 )) - TM_YEAR_BASE;
         g_rtcTime = gmktime(&utm);
       }
       Coproc_temp = Co_proc_status[8];
diff --git a/radio/src/targets/sky9x/rtc_driver.cpp b/radio/src/targets/sky9x/rtc_driver.cpp
index 0035aa30e..a70a6cdf7 100644
--- a/radio/src/targets/sky9x/rtc_driver.cpp
+++ b/radio/src/targets/sky9x/rtc_driver.cpp
@@ -246,8 +246,8 @@ void rtcSetTime(const struct gtm * t)
   I2CTime.Time[2] = t->tm_hour ;
   I2CTime.Time[3] = t->tm_mday ;
   I2CTime.Time[4] = t->tm_mon+1 ;
-  I2CTime.Time[5] = (uint8_t) (t->tm_year+1900);
-  I2CTime.Time[6] = (t->tm_year+1900) >> 8;
+  I2CTime.Time[5] = (uint8_t) (t->tm_year+TM_YEAR_BASE);
+  I2CTime.Time[6] = (t->tm_year+TM_YEAR_BASE) >> 8;
 #if defined(REVX)
   writeRTC((uint8_t *)&I2CTime.Time[0]) ;
 #elif defined(COPROCESSOR)
diff --git a/radio/src/telemetry/telemetry.cpp b/radio/src/telemetry/telemetry.cpp
index 9977528d4..c93c65284 100644
--- a/radio/src/telemetry/telemetry.cpp
+++ b/radio/src/telemetry/telemetry.cpp
@@ -470,7 +470,7 @@ void logTelemetryWriteStart()
   if (lastTime != newTime) {
     struct gtm utm;
     gettime(&utm);
-    f_printf(&g_telemetryFile, "\r\n%4d-%02d-%02d,%02d:%02d:%02d.%02d0:", utm.tm_year+1900, utm.tm_mon+1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec, g_ms100);
+    f_printf(&g_telemetryFile, "\r\n%4d-%02d-%02d,%02d:%02d:%02d.%02d0:", utm.tm_year+TM_YEAR_BASE, utm.tm_mon+1, utm.tm_mday, utm.tm_hour, utm.tm_min, utm.tm_sec, g_ms100);
     lastTime = newTime;
   }
 }