ESP32 - RTC off by 2hrs when used deepsleep

[vangaveeti]

Hello, I've mixed SimpleTime and DeepSleep TimerWakeUp examples and created the below program that prints time from the internal RTC every 20 secs. The time is printed correctly when I first start the ESP32, but after the first sleep cycle, the time is off by 2 hrs and stays off consistently. I couldn't figure out the problem. Can someone please help?

My Code:

#include <WiFi.h>
#include "time.h"
#include "WiFi_credentials.h"

const char* ntpServer = "pool.ntp.org";
const long  gmtOffset_sec = 3600;
const int   daylightOffset_sec = 3600;

#define uS_TO_S_FACTOR 1000000ULL  /* Conversion factor for micro seconds to seconds */
#define TIME_TO_SLEEP  20        /* Time ESP32 will go to sleep (in seconds) */

enum states_main {RST , TIME};
RTC_DATA_ATTR uint8_t state = RST;

void printLocalTime()
{
  struct tm timeinfo;
  if(!getLocalTime(&timeinfo)){
    Serial.println("Failed to obtain time");
    return;
  }
  Serial.println(&timeinfo, "%A, %B %d %Y %H:%M:%S");
}

void sleep(){
  esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);
  Serial.println("Setup ESP32 to sleep for every " + String(TIME_TO_SLEEP) +
  " Seconds");
  
  Serial.println("Going to sleep now");
  Serial.println("---------------------------------------------");
  Serial.println(" ");
  Serial.flush();
  esp_deep_sleep_start();
}


void setup()
{
  Serial.begin(115200);
  delay(100);
  
  switch(state) {
    
    case RST:
      Serial.println("In RESET");
      //connect to WiFi
      Serial.printf("Connecting to %s ", ssid);
      WiFi.begin(ssid, password);
      while (WiFi.status() != WL_CONNECTED) {
          delay(500);
          Serial.print(".");
      }
      Serial.println(" CONNECTED");
  
      //init and get the time
      configTime(gmtOffset_sec, daylightOffset_sec, ntpServer);
      printLocalTime();
    
      //disconnect WiFi as it's no longer needed
      WiFi.disconnect(true);
      WiFi.mode(WIFI_OFF);
      state = TIME;
      sleep();
    break;
    
    case TIME:
      Serial.println("In TIME");
      printLocalTime();
      sleep();
    break;
  
  }
}

void loop()
{
  
}

Output from the Serial Terminal

In RESET
Connecting to WiFi ... CONNECTED
Tuesday, August 17 2021 19:04:33
Setup ESP32 to sleep for every 20 Seconds
Going to sleep now
---------------------------------------------
 
ets Jun  8 2016 00:22:57

rst:0x5 (DEEPSLEEP_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1216
ho 0 tail 12 room 4
load:0x40078000,len:10944
load:0x40080400,len:6388
entry 0x400806b4
In TIME
Tuesday, August 17 2021 17:04:53
Setup ESP32 to sleep for every 20 Seconds
Going to sleep now
---------------------------------------------
 
ets Jun  8 2016 00:22:57

rst:0x5 (DEEPSLEEP_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1216
ho 0 tail 12 room 4
load:0x40078000,len:10944
load:0x40080400,len:6388
entry 0x400806b4
In TIME
Tuesday, August 17 2021 17:05:14
Setup ESP32 to sleep for every 20 Seconds
Going to sleep now
---------------------------------------------
 
ets Jun  8 2016 00:22:57

rst:0x5 (DEEPSLEEP_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1216
ho 0 tail 12 room 4
load:0x40078000,len:10944
load:0x40080400,len:6388
entry 0x400806b4
In TIME
Tuesday, August 17 2021 17:05:34
Setup ESP32 to sleep for every 20 Seconds
Going to sleep now
---------------------------------------------
 
ets Jun  8 2016 00:22:57

rst:0x5 (DEEPSLEEP_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1216
ho 0 tail 12 room 4
load:0x40078000,len:10944
load:0x40080400,len:6388
entry 0x400806b4
In TIME
Tuesday, August 17 2021 17:05:54
Setup ESP32 to sleep for every 20 Seconds
Going to sleep now
---------------------------------------------

As we can see the correct time was 19:04:33 but after the first deep sleep cycle, it got changed to 17:04:53 instead of 19:04:53. Can someone please tell me why this is happening?