This code allows you to add the date and time to your SD card log files generated by an Arduino.

Code to add Date and Time to files written to SD cards.ino

#include <SD.h>

File file;
const uint8_t CS = 10; // SD chip select

    // YOUR SKETCH SHOULD UPDATE THESE SIX VALUES
    // EACH TIME BEFORE CREATING YOUR SD CARD FILE
unsigned int year = 2015;
byte month = 6;      
byte day = 18;
byte hour = 7;
byte minute = 8;
byte second = 9;

void dateTime(uint16_t* date, uint16_t* time)
{
  *date = FAT_DATE(year, month, day);
  *time = FAT_TIME(hour, minute, second);
}

void setup()
{
  Serial.begin(9600);
  
      // THIS LINE SETS YOUR SKETCH TO SAVE YOUR
      // TIME AND DATE INTO ANY FILE YOU CREATE.
  SdFile::dateTimeCallback(dateTime);
  
  if (!SD.begin(CS))
  {
    Serial.println("SD.begin failed");
    while(1);
  }
  file = SD.open("TEST_IT.TXT", FILE_WRITE);
  file.close();
  Serial.println("Done");
}

void loop() {}