How to switch between 12/24 hour format RTC DS1307

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unsigned short read_ds1307(unsigned short address)
      {
        unsigned short read_data;
        I2C1_Start();
        I2C1_Wr(0xD0); //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
        I2C1_Wr(address);
        I2C1_Repeated_Start();
        I2C1_Wr(0xD1); //0x68 followed by 1 --> 0xD1
        read_data=I2C1_Rd(0);
        I2C1_Stop();
        return(read_data);
      }
      void write_ds1307(unsigned short address,unsigned short write_data)
      {
        I2C1_Start(); // issue I2C start signal
        //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
        I2C1_Wr(0xD0); // send byte via I2C (device address + W)
        I2C1_Wr(address); // send byte (address of DS1307 location)
        I2C1_Wr(write_data); // send data (data to be written)
        I2C1_Stop(); // issue I2C stop signal
      }
 
      unsigned char MSB(unsigned char x)           //Display Most Significant Bit of BCD number
      {
        return ((x >> 4) + '0');
      }
      unsigned char  LSB(unsigned char x)          //Display Least Significant Bit of BCD number
      {
        return ((x & 0x0F) + '0');
      }
       void main()
      {
       I2C1_Init(100000);     //DS1307 I2C is running at 100KHz
       PORTA = 0 ;
       ADCON1 = 0x06;         // Configure all ports with analog function as digital
       TRISA = 0b000111;
       TRISB = 0 ;
       TRISC = 0b00011000 ;
       PORTC = 0 ;
       PORTB = 0 ;
       I2C1_Start() ;
       I2C1_wr(0x0D) ;
       I2C1_wr(0) ;
       I2C1_wr(0x80) ;
       I2C1_wr(0x51) ;
       I2C1_wr(0x71) ;
       I2C1_Stop() ;
       write_ds1307(7,0x50) ; // SQWE output 1Hz
      write_ds1307(2,0x40) ; // <========  time set for 12 hour mode
       oldstate = 1 ;       
 
       do {. . . . 
 
      . . . .         }
            second = read_ds1307(0);
            minute = read_ds1307(1);
            hour = read_ds1307(2);
            hr = hour & 0b00011111;