diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index 112775c..8f09191 100644
--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -207,7 +207,8 @@
 	tm->tm_hour = bcd2bin(regs[2] & 0x3f);
 	tm->tm_mday = bcd2bin(regs[3] & 0x3f);
 	tm->tm_wday = regs[4] & 0x7;
-	tm->tm_mon = bcd2bin(regs[5] & 0x1f);
+	/* rtc month is 1 - 12 */
+	tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
 	tm->tm_year = bcd2bin(regs[6]) + 100;
 
 	return rtc_valid_tm(tm);
@@ -230,7 +231,8 @@
 	regs[3] = bin2bcd(tm->tm_hour);
 	regs[4] = bin2bcd(tm->tm_mday);
 	regs[5] = tm->tm_wday;
-	regs[6] = bin2bcd(tm->tm_mon);
+	/* rtc month is 1 - 12 */
+	regs[6] = bin2bcd(tm->tm_mon + 1);
 	regs[7] = bin2bcd(tm->tm_year - 100);
 
 	msg.addr = client->addr;