diff --git a/G0:G070/RTC/README b/G0:G070/RTC/README
index 351b779..c977189 100644
--- a/G0:G070/RTC/README
+++ b/G0:G070/RTC/README
@@ -2,9 +2,11 @@ Simplest work with RTC
 
 Proto:
 
+C - set/print calibration ticks (-511..+512) to each 2^20 ticks
+Sd - set date (YY MM DD Weekday)
+St - set time (HH MM SS)
 t - print current Tms
-T - print current Time like 'Mon Jan 1 00:05:19 2001'
-
+T - print current Time
 
 Button press - print current time @ usart3
 
diff --git a/G0:G070/RTC/main.c b/G0:G070/RTC/main.c
index e680532..6c2c9da 100644
--- a/G0:G070/RTC/main.c
+++ b/G0:G070/RTC/main.c
@@ -65,7 +65,7 @@ int main(void){
         int wasbo = 0;
         char *rcv = usart3_getline(&wasbo);
         if(wasbo) usart3_sendstr("Buffer overflow occured @ last message\n");
-        if(rcv) rcv = parse_cmd(rcv);
+        if(rcv) rcv = (char*)parse_cmd(rcv);
         if(rcv) usart3_sendstr(rcv);
     }
 }
diff --git a/G0:G070/RTC/proto.c b/G0:G070/RTC/proto.c
index dca5aac..3365901 100644
--- a/G0:G070/RTC/proto.c
+++ b/G0:G070/RTC/proto.c
@@ -26,6 +26,9 @@
 extern volatile uint32_t Tms;
 
 const char *helpstring =
+        "C - set/print calibration ticks (-511..+512) to each 2^20 ticks\n"
+        "Sd - set date (YY MM DD Weekday)\n"
+        "St - set time (HH MM SS)\n"
         "t - print current Tms\n"
         "T - print current Time\n"
 ;
@@ -36,6 +39,7 @@ TRUE_INLINE void putch(char x){
 
 static const char *weekdays[] = {"Mon", "Tue", "Wed", "Thur", "Fri", "Sat", "Sun"};
 static const char *months[] = {"Jan", "Feb", "Mar", "Apr", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"};
+static const char *OK = "OK\n";
 
 static void prezero(uint8_t x){
     if(x < 10){ putch('0'); putch('0' + x);}
@@ -45,7 +49,7 @@ static void prezero(uint8_t x){
 void print_curtime(){
     rtc_t t;
     get_curtime(&t);
-    USND(weekdays[t.day - 1]);
+    USND(weekdays[t.weekday - 1]);
     putch(' ');
     USND(months[t.month - 1]);
     putch(' ');
@@ -60,13 +64,75 @@ void print_curtime(){
     putch('\n');
 }
 
-char *parse_cmd(char *buf){
-    // "long" commands
-/*    switch(*buf){
-    }*/
-    // "short" commands
-    if(buf[1]) return buf; // echo wrong data
+static int readNu8(const char *buf, uint8_t *arr, int maxlen){
+    uint32_t D;
+    const char *nxt;
+    int N = 0;
+    while((nxt = getnum(buf, &D)) && nxt != buf && N < maxlen){
+        buf = nxt;
+        if(D > 0xff){
+            USND("Value too large\n");
+            return N;
+        }
+        arr[N++] = (uint8_t) D&0xff;
+    }
+    return N;
+}
+
+TRUE_INLINE const char* setdatetime(const char *buf){
+    buf = omit_spaces(buf);
+    uint8_t array[4];
+    rtc_t r;
     switch(*buf){
+        case 'd': // set date
+            if(4 != readNu8(buf+1, array, 4))
+                return "Format: YY MM DD Weekday (monday is 1)\n";
+            r.year = array[0]; 
+            r.month = array[1];
+            r.day = array[2];
+            r.weekday = array[3];
+            if(!rtc_setdate(&r)) return "Wrong date format\n";
+        break;
+        case 't': // set time
+            if(3 != readNu8(buf+1, array, 3))
+                return "Format: HH MM SS\n";
+            r.hour = array[0];
+            r.minute = array[1];
+            r.second = array[2];
+            if(!rtc_settime(&r)) return "Wrong time format\n";
+        break;
+        default:
+            return "Sd -> set date; St -> set time\n";
+    }
+    return OK;
+}
+
+TRUE_INLINE const char *setcal(const char *buf){
+    int32_t v;
+    if(buf == getint(buf, &v)){
+        USND("Calibration value: ");
+        USND(i2str(rtc_getcalib()));
+        putch('\n');
+        return NULL;
+    } 
+    if(!rtc_setcalib(v)) return "Enter value: -511..+512\n";
+    return OK;
+}
+
+const char *parse_cmd(char *buf){
+    const char *x = omit_spaces(buf);
+    // "long" commands
+    switch(*x){
+        case 'S':
+            return setdatetime(x + 1);
+        break;
+        case 'C':
+            return setcal(x + 1);
+        break;
+    }
+    // "short" commands
+    if(x[1]) return x; // echo wrong data
+    switch(*x){
         case 't':
             USND("T=");
             USND(u2str(Tms));
diff --git a/G0:G070/RTC/proto.h b/G0:G070/RTC/proto.h
index a39fa1f..88207a2 100644
--- a/G0:G070/RTC/proto.h
+++ b/G0:G070/RTC/proto.h
@@ -18,5 +18,5 @@
 
 #pragma once
 
-char *parse_cmd(char *buf);
+const char *parse_cmd(char *buf);
 void print_curtime();
diff --git a/G0:G070/RTC/rtc.bin b/G0:G070/RTC/rtc.bin
index 10bc3ba..0bb1fae 100755
Binary files a/G0:G070/RTC/rtc.bin and b/G0:G070/RTC/rtc.bin differ
diff --git a/G0:G070/RTC/rtc.c b/G0:G070/RTC/rtc.c
index 541d103..8ba2c06 100644
--- a/G0:G070/RTC/rtc.c
+++ b/G0:G070/RTC/rtc.c
@@ -24,6 +24,56 @@
 #define WAITWHILE(x)  do{register uint32_t StartUpCounter = 0; while((x) && (++StartUpCounter < 0xffffff)){nop();}}while(0)
 #endif
 
+static const uint8_t maxdays[12] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+
+// i - in, r - rest of divide
+#if 0
+static uint16_t div10s(uint16_t i, uint16_t *r){ // divide by 10
+    uint32_t u = i;
+    u *= 52429;
+    u >>= 19;
+    if(r) *r = i - 10*u;
+    return (uint16_t)u;
+}
+#endif
+static uint8_t div10b(uint8_t i, uint8_t *r){ // divide by 10
+    uint32_t u = i;
+    u *= 52429;
+    u >>= 19;
+    if(r) *r = i - 10*u;
+    return (uint8_t)u;
+}
+
+static uint8_t DEC2BCD(uint8_t x){
+    uint8_t d, r;
+    d = div10b(x, &r);
+    return (d << 4 | r);
+}
+
+int rtc_setdate(rtc_t *d){
+    if(d->year > 99) return FALSE;
+    if(d->month > 12 || d->month == 0) return FALSE;
+    if(d->day > maxdays[d->month - 1] || d->day == 0) return FALSE;
+    if(d->month == 2 && d->day == 29 && (d->year & 4) != 4) return FALSE; // not leap year
+    if(d->weekday > 7 || d->weekday == 0) return FALSE;
+    RTC->ICSR |= RTC_ICSR_INIT;
+    WAITWHILE(!(RTC->ICSR & RTC_ICSR_INITF));
+    RTC->DR = DEC2BCD(d->year) << RTC_DR_YU_Pos | d->weekday << RTC_DR_WDU_Pos | DEC2BCD(d->month) << RTC_DR_MU_Pos | DEC2BCD(d->day) << RTC_DR_DU_Pos;
+    RTC->ICSR &= ~RTC_ICSR_INIT;
+    return TRUE;
+}
+
+int rtc_settime(rtc_t *t){
+    if(t->hour > 23) return FALSE;
+    if(t->minute > 59) return FALSE;
+    if(t->second > 59) return FALSE;
+    RTC->ICSR |= RTC_ICSR_INIT;
+    WAITWHILE(!(RTC->ICSR & RTC_ICSR_INITF));
+    RTC->TR = DEC2BCD(t->hour) << RTC_TR_HU_Pos | DEC2BCD(t->minute) << RTC_TR_MNU_Pos | DEC2BCD(t->second) << RTC_TR_SU_Pos;
+    RTC->ICSR &= ~RTC_ICSR_INIT;
+    return TRUE;
+}
+
 void rtc_setup(){
     PWR->CR1 |= PWR_CR1_DBP; // disable RTC write protection
     // turn on LSE and switch RTC to it
@@ -59,3 +109,25 @@ void get_curtime(rtc_t *t){
     t->weekday = (r >> RTC_DR_WDU_Pos) & 0x7;
     t->year = BCDu(RTC_DR_YU_Pos) + 10 * BCDu(RTC_DR_YT_Pos);
 }
+
+// set calibration value
+int rtc_setcalib(int calval){
+    if(calval < -511 || calval > 512) return FALSE;
+    uint32_t calp = 0, calm = 0;
+    if(calval < 0)  calm = -calval;
+    else if(calval > 0){
+        calp = RTC_CALR_CALP;
+        calm = 512 - calval;
+    }
+    // unlock RCC
+    RTC->WPR = 0xCA;
+    RTC->WPR = 0x53;
+    RTC->CALR = calp | calm;
+    return 1;
+}
+
+int rtc_getcalib(){
+    int calval = (RTC->CALR & RTC_CALR_CALP) ? 512 : 0;
+    calval -= RTC->CALR & 0x1ff;
+    return calval;
+}
diff --git a/G0:G070/RTC/rtc.h b/G0:G070/RTC/rtc.h
index e5f8c8c..81f695a 100644
--- a/G0:G070/RTC/rtc.h
+++ b/G0:G070/RTC/rtc.h
@@ -34,3 +34,7 @@ typedef struct{
 void rtc_setup();
 
 void get_curtime(rtc_t *t);
+int rtc_setdate(rtc_t *d);
+int rtc_settime(rtc_t *t);
+int rtc_setcalib(int calval);
+int rtc_getcalib();
\ No newline at end of file
diff --git a/G0:G070/RTC/strfunc.c b/G0:G070/RTC/strfunc.c
index c52785e..89b898b 100644
--- a/G0:G070/RTC/strfunc.c
+++ b/G0:G070/RTC/strfunc.c
@@ -60,8 +60,11 @@ static char *_2str(uint32_t  val, uint8_t minus){
         *(--bufptr) = '0';
     }else{
         while(val){
-            *(--bufptr) = val % 10 + '0';
-            val /= 10;
+            uint32_t x = val / 10;
+            *(--bufptr) = (val - 10*x) + '0';
+            val = x;
+            //*(--bufptr) = val % 10 + '0';
+            //val /= 10;
         }
     }
     if(minus) *(--bufptr) = '-';
@@ -113,12 +116,12 @@ char *uhex2str(uint32_t val){
  * @param buf - string
  * @return - pointer to first character in `buf` > ' '
  */
-char *omit_spaces(const char *buf){
+const char *omit_spaces(const char *buf){
     while(*buf){
         if(*buf > ' ') break;
         ++buf;
     }
-    return (char*)buf;
+    return buf;
 }
 
 /**
@@ -127,7 +130,7 @@ char *omit_spaces(const char *buf){
  * @param N - number read
  * @return Next non-number symbol. In case of overflow return `buf` and N==0xffffffff
  */
-static char *getdec(const char *buf, uint32_t *N){
+static const char *getdec(const char *buf, uint32_t *N){
     char *start = (char*)buf;
     uint32_t num = 0;
     while(*buf){
@@ -144,11 +147,11 @@ static char *getdec(const char *buf, uint32_t *N){
         ++buf;
     }
     *N = num;
-    return (char*)buf;
+    return buf;
 }
 // read hexadecimal number (without 0x prefix!)
-static char *gethex(const char *buf, uint32_t *N){
-    char *start = (char*)buf;
+static const char *gethex(const char *buf, uint32_t *N){
+    const char *start = buf;
     uint32_t num = 0;
     while(*buf){
         char c = *buf;
@@ -173,11 +176,11 @@ static char *gethex(const char *buf, uint32_t *N){
         ++buf;
     }
     *N = num;
-    return (char*)buf;
+    return buf;
 }
 // read octal number (without 0 prefix!)
-static char *getoct(const char *buf, uint32_t *N){
-    char *start = (char*)buf;
+static const char *getoct(const char *buf, uint32_t *N){
+    const char *start = (char*)buf;
     uint32_t num = 0;
     while(*buf){
         char c = *buf;
@@ -193,11 +196,11 @@ static char *getoct(const char *buf, uint32_t *N){
         ++buf;
     }
     *N = num;
-    return (char*)buf;
+    return buf;
 }
 // read binary number (without b prefix!)
-static char *getbin(const char *buf, uint32_t *N){
-    char *start = (char*)buf;
+static const char *getbin(const char *buf, uint32_t *N){
+    const char *start = (char*)buf;
     uint32_t num = 0;
     while(*buf){
         char c = *buf;
@@ -213,7 +216,7 @@ static char *getbin(const char *buf, uint32_t *N){
         ++buf;
     }
     *N = num;
-    return (char*)buf;
+    return buf;
 }
 
 /**
@@ -223,9 +226,9 @@ static char *getbin(const char *buf, uint32_t *N){
  * @return pointer to first non-number symbol in buf
  *      (if it is == buf, there's no number or if *N==0xffffffff there was overflow)
  */
-char *getnum(const char *txt, uint32_t *N){
-    char *nxt = NULL;
-    char *s = omit_spaces(txt);
+const char *getnum(const char *txt, uint32_t *N){
+    const char *nxt = NULL;
+    const char *s = omit_spaces(txt);
     if(*s == '0'){ // hex, oct or 0
         if(s[1] == 'x' || s[1] == 'X'){ // hex
             nxt = gethex(s+2, N);
@@ -247,6 +250,22 @@ char *getnum(const char *txt, uint32_t *N){
     return nxt;
 }
 
+// get signed integer
+const char *getint(const char *txt, int32_t *I){
+    const char *s = omit_spaces(txt);
+    int32_t sign = 1;
+    uint32_t U;
+    if(*s == '-'){
+    	sign = -1;
+    	++s;
+    }
+    const char *nxt = getnum(s, &U);
+    if(nxt == s) return txt;
+    if(U & 0x80000000) return txt; // overfull
+    *I = sign * (int32_t)U;
+    return nxt;
+}
+
 /*
 void mymemcpy(char *dest, const char *src, int len){
     if(len < 1) return;
diff --git a/G0:G070/RTC/strfunc.h b/G0:G070/RTC/strfunc.h
index a6662d5..cdb27b5 100644
--- a/G0:G070/RTC/strfunc.h
+++ b/G0:G070/RTC/strfunc.h
@@ -21,9 +21,10 @@
 #include <string.h>
 
 void hexdump(int (*sendfun)(const char *s), uint8_t *arr, uint16_t len);
-char *u2str(uint32_t val);
-char *i2str(int32_t i);
-char *uhex2str(uint32_t val);
-char *getnum(const char *txt, uint32_t *N);
-char *omit_spaces(const char *buf);
+const char *u2str(uint32_t val);
+const char *i2str(int32_t i);
+const char *uhex2str(uint32_t val);
+const char *getnum(const char *txt, uint32_t *N);
+const char *omit_spaces(const char *buf);
+const char *getint(const char *txt, int32_t *I);
 //void mymemcpy(char *dest, const char *src, int len);