DST_RTC

library for automatically adjusting RTC time for daylight saving time (DST)

requires RTClib

Function to figure out if we're in Daylight Saving Time, then adding an hour if we are in DST.
adapted from nseidle https://github.com/nseidle/Daylight_Savings_Time_Example/blob/master/Daylight_Savings_Time_Example.ino
and further adapted from Andy Doro https://github.com/andydoro/DST_RTC

This algorithm is programmed to observe Daylight Saving Time in the United States, where as of the time of writing DST is observed between the second Sunday in March and the first Sunday in November.

The rules for DST vary by country and territory.
https://en.wikipedia.org/wiki/Daylight_saving_time_by_country

The new version requires explicit definition of whether to use US or EU rules.

This method checks whether its 2am or not when the time change officially occurs (this addition by Peter Bradley).

Addition Peter Bradley

• Added 2:00 AM time change for the USA.
• In the European Union, Summer Time begins and ends at 1:00 a.m. Universal Time (Greenwich Mean Time).
• For most of Europe DST usually begins on the last Sunday of March at 2:00 AM local time and ends on the last Sunday of October at 2:00 AM local time. The last Sunday of the month of March and October must always be on or after the 25th.

Installation

From the Library Manager

1. Launch the Arduino IDE and navigate to Sketch → Include Library → Manage Libraries.
2. In the library manager, scroll to DST_RTC or enter the name into the search field.
3. Click on the library, then click on the Install button.

From the ZIP file

1. Download the ZIP file.
2. Launch the Arduino IDE and navigate to Sketch → Include Library → Add .ZIP Library.... From the prompt, select the ZIP just downloaded.