Hey!! It will be great if you can add date and month functions as well.

[shariramani]

Please add date and month function. May be you can add something like
13 April 1974, Wednesday

[sheffieldnikki]

I've just written a getFormattedDate() method for my own use, that outputs an ISO 8601 date/time string. Here it is, in case anyone finds it useful.

Aside: there is a line to draw between having a lean, minimal library with limited functionality, and adding so many features that you have a bloated mess that would be better provided by using separate libraries... but where to draw it?

NTPClient.h:

/**
 * @return secs argument (or 0 for current date) formatted to ISO 8601
 * like `2004-02-12T15:19:21+00:00`
 */
String getFormattedDate(unsigned long secs = 0);

NTPClient.cpp:

#define LEAP_YEAR(Y)     ( (Y>0) && !(Y%4) && ( (Y%100) || !(Y%400) ) )

// Based on https://github.com/PaulStoffregen/Time/blob/master/Time.cpp
// currently assumes UTC timezone, instead of using this->_timeOffset
String NTPClient::getFormattedDate(unsigned long secs) {
  unsigned long rawTime = (secs ? secs : this->getEpochTime()) / 86400L;  // in days
  unsigned long days = 0, year = 1970;
  uint8_t month;
  static const uint8_t monthDays[]={31,28,31,30,31,30,31,31,30,31,30,31};

  while((days += (LEAP_YEAR(year) ? 366 : 365)) <= rawTime)
    year++;
  rawTime -= days - (LEAP_YEAR(year) ? 366 : 365); // now it is days in this year, starting at 0
  days=0;
  for (month=0; month<12; month++) {
    uint8_t monthLength;
    if (month==1) { // february
      monthLength = LEAP_YEAR(year) ? 29 : 28;
    } else {
      monthLength = monthDays[month];
    }
    if (rawTime < monthLength) break;
    rawTime -= monthLength;
  }
  String monthStr = ++month < 10 ? "0" + String(month) : String(month); // jan is month 1  
  String dayStr = ++rawTime < 10 ? "0" + String(rawTime) : String(rawTime); // day of month  
  return String(year) + "-" + monthStr + "-" + dayStr + "T" + this->getFormattedTime(secs ? secs : 0) + "Z";
}