Which is better (dst check function)

Projects Programming
1

I always used similar dst check function like this one:


<code>
long adjustDstEurope(long epoch)
{
  // last sunday of march
  int beginDSTDate= (31 - (5* year(epoch) /4 + 4) % 7);
  int beginDSTMonth=3;
  //last sunday of october
  int endDSTDate= (31 - (5 * year(epoch) /4 + 1) % 7);
  int endDSTMonth=10;
  // DST is valid as:
  if (((month(epoch) > beginDSTMonth) && (month(epoch) < endDSTMonth))
    || ((month(epoch) == beginDSTMonth) && (day(epoch) >= beginDSTDate))
    || ((month(epoch) == endDSTMonth) && (day(epoch) < endDSTDate)))
    return true; // DST europe = GMT +2
  else return false; // nonDST europe = GMT +1
}
</code>

but i never understood the logic of previous code and did not write it myself.
but now i wrote this:

<code>
boolean dst_check(long epoch) {
  //day();             // the day now (1-31)
  //weekday();         // day of the week (1-7), Sunday is day 1
  if (day(epoch)>= 24+weekday(epoch) && month(epoch) == 3) ||
     (month(epoch) > 3 && month(epoch) < 10) ||
     (day(epoch)< 24+weekday(epoch) && month(epoch) == 10 )
      return true; // DST europe = GMT +2
      else return false; // nonDST europe = GMT +1
      
  }
</code>

i want to use smallest code as possible and not extra libs.
Which is best?

2

Which Arduino board? ESP32 does all of that for you in the background. No effort required on your part.

3

Depends what you mean by, "best"... :thinking:

IMO, "best" (if possible) is to not use DST at all - do everything in UTC.

Why do you feel you need DST in your Arduino?

Administrations may alter (or abandon) DST on a whim - so no algorithm can be completely reliable.

If you really must do DST on the device, and have a comms link, then signal DST over that link.

4

It's a esp01.
The DST (European summer/wintertime) is needed for accurate logging and timekeeping events.
Here in Central Europe we go the last Sunday of March and October to +2 instead +1

utc time retrieved by a ntc server every hour.

But is my function not better than the 1st function?
It's hard to test, only once each month :wink: I should change the month number and i can test it betwen next Saturday and Sunday.

Official the DST changes on 02:00 and 03:00 AM. But for the working of the programming has not much of a impact.

5

The built-in functions mentioned by @gfvalvo also work for esp8266 including esp-01. Very simple to use.

https://werner.rothschopf.net/202011_arduino_esp8266_ntp_en.htm

1 Like
6

You don't need DST for that - just work in UTC!

You mean NTP?

Indeed it is - that's another good reason not to do it!

7

See post#9 in this thread.
Change the configTime values to where you live.
The timezone string can be found here. You should pick an NTP server in your country.
Leo..

8

as already mentioned: use the functionality of the ESP core.
The english page was already posted,
if you need it in German:
ESP8266 NTP Abfrage mit Sommerzeit / Winterzeit (NodeMCU, Wemos D1) (rothschopf.net)

9

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