Humidity logger

sketch.ino

#include "DHT.h"
#include "SD.h"
#include "Wire.h"

#define DHTTYPE DHT22
#define DHTPIN 4

DHT dht(DHTPIN, DHTTYPE);
File logFile;

void setup() {
  Serial.begin(9600);
  Serial.print("Initializing SD card...");

  pinMode(10, OUTPUT);

  if (!SD.begin(10)) {
    Serial.println("initialization failed!");
    return;
  }

  Serial.println("initialization done.");

  dht.begin();

  // Setup RTC
  Wire.begin();

  Wire.beginTransmission(0x68); // address DS3231
  Wire.write(0x0E);             // select register
  Wire.write(0b00011100);       // write register bitmap, bit 7 is /EOSC
  Wire.endTransmission();
}

void loop() {
  delay(600000);

  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  float t = dht.readTemperature(true);

  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  logFile = SD.open("boat.txt", FILE_WRITE);

  if (logFile) {
    Wire.beginTransmission(0x68); // 0x68 is DS3231 device address
    Wire.write((byte)0);          // start at register 0
    Wire.endTransmission();
    Wire.requestFrom(0x68, 7);    // request 7 bytes (seconds, minutes, hours, day of week, day of month, month and year)

    int second = bcdToDec(Wire.read()); // get seconds
    int minute = bcdToDec(Wire.read()); // get minutes
    int hour = bcdToDec(Wire.read());   // get hours
    int dow = bcdToDec(Wire.read());    // get day of week
    int dom = bcdToDec(Wire.read());    // get day of month
    int month = bcdToDec(Wire.read());  // get month
    int year = bcdToDec(Wire.read());   // get year

    Serial.print(year + 2000); Serial.print("-"); Serial.print(month); Serial.print("-"); Serial.print(dom); Serial.print(" ");
    Serial.print(hour); Serial.print(":"); Serial.print(minute); Serial.print(":"); Serial.print(second); Serial.print(",");
    Serial.print(h); Serial.print(","); Serial.println(t);

    logFile.print(year + 2000); logFile.print("-"); logFile.print(month); logFile.print("-"); logFile.print(dom); logFile.print(" ");
    logFile.print(hour); logFile.print(":"); logFile.print(minute); logFile.print(":"); logFile.print(second); logFile.print(",");
    logFile.print(h); logFile.print(","); logFile.println(t);
  }

  logFile.close();
}

// Convert normal decimal numbers to binary coded decimal
byte decToBcd(byte val) {
  return( (val/10*16) + (val%10) );
}

// Convert binary coded decimal to normal decimal numbers
byte bcdToDec(byte val) {
  return( (val/16*10) + (val%16) );
}

I got this far with a similar code:
#include "dht.h"
#include "SD.h"
#include "Wire.h"

dht DHT;

#define DHTTYPE DHT22
#define DHTPIN 3

DHT dht(DHTPIN, DHTTYPE);

'DHT' does not name a type, any suggestions?