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Would anyone find the following useful?

I'm a bit of a novice but I wrote the following to set British Summer Time(BST - Day Light Savings) - this is assuming you have already got GMT from a server.

It seems to work ok.

//------------------..------------------------------------------------
// British summer time
//------------------------------------------------------------------
void setDayLightSavings(int bst){
  DateTime now = RTC.now();

  DateTime bstStart = DateTime(now.year(), 3, 31, 1,0,0); // End of march
  int lastSun = bstStart.dayOfWeek();
  bstStart = DateTime(now.year(),3,31-lastSun,1,0,0); // Last Sunday in March

  DateTime bstStop = DateTime(now.year(), 10, 31, 1,0,0); // End of October
  lastSun = bstStop.dayOfWeek();
  bstStop = DateTime(now.year(),10,31-lastSun,1,0,0); // Last Sunday in October

  // Date comparison by converting the month, day, and hour to a single long integer
  // i.e. March 25 01:00= (3*10000)+(25*100)+01 = 32501
  //      October 28 01:00 = (10*10000)+(28*100)+01 = 102801
  // We then use the same on the current date to see if it falls between the two numbers
  long s = ((long) bstStart.month()*10000)+(bstStart.day()*100+bstStart.hour());
  long e = ((long) bstStop.month()*10000)+(bstStop.day()*100)+bstStop.hour();
  long n = ((long) now.month()*10000)+(now.day()*100)+now.hour();
  if ( (n>=s) && (n<e)){
    RTC.adjust(DateTime(now.year(), now.month(), now.day(), now.hour()+1, now.minute(), now.second()));
    bst=1;
    }else{bst=0;}
}

"bst" is just a return to indicate if BST is active...

I should have added that set the date and time in the first place using the following from a server header:

  get_header_line(2,off);      // Get the date and time from the header
  Serial.println(line_buf);    // Print out the date and time

  char thedate[12];
  thedate[0]=line_buf[14];
  thedate[1]=line_buf[15];
  thedate[2]=line_buf[16];
  thedate[3]=' ';
  thedate[4]=line_buf[11];
  thedate[5]=line_buf[12];
  thedate[6]=' ';
  thedate[7]=line_buf[18];
  thedate[8]=line_buf[19];
  thedate[9]=line_buf[20];
  thedate[10]=line_buf[21];
  thedate[11]='\0';
 
  char thetime[9];
  thetime[0]=line_buf[23];
  thetime[1]=line_buf[24];
  thetime[2]=line_buf[25];
  thetime[3]=line_buf[26];
  thetime[4]=line_buf[27];
  thetime[5]=line_buf[28];
  thetime[6]=line_buf[29];
  thetime[7]=line_buf[30];
  thetime[8]='\0';
 
  RTC.adjust(DateTime(thedate,thetime));

Please let me know if anything is wrong...