Simple rule based Daylight Saving Time adjust library that implements DST aware version of the esp8266 time() function.
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README.md

simpleDSTadjust

ESP8266 Automatic Daylight Saving Time (DST) adjust library.

This library implements missing DST functionality by implementing a wrapper API to the built-in time() function. It uses simple rules to define the start and end of DST. Rules work for most contries that observe DST.

Caution: DST rules may change in the future if you hardcode the rules.

Portions of code adapted from:

  • Arduino Timezone Library by Jack Christensen
  • Arduino Time Library by Paul Stoffregen

Quick Start

Installing

You can install by using the Arduino Library manager and searching for simpleDSTadjust or by downloading the contents of the library as a .zip file and using the Arduino Library Manager to add the .zip file.

Examples

ntpTimedemo_DST

An example is included with the library that shows how to use the built-in LWIP sntp client to get the time from an NTP server and adjust for daylight saving time. This example shows how to write out the time in a 12 hour format, which could be easily adapted for a 24 hour format. It includes rules for US/Eastern (New York) and Australia/Eastern (Sydney) timezones which can be changes to other other country/city timezones. It also shows how to implement a timer to update the NTP time with an interval greater than 2 hours.

Squix78 Weather Station Example

See the WeatherStationDemoExtendedDST example for a full implementation including selectable locales, 12/24 hour clock formats and more.

Library Usage

Include the library in your sketch

#include <simpleDSTadjust.h>

Define the DST rules that you want

//US Eastern Time Zone (New York, Boston)
struct dstRule StartRule = {"EDT", Second, Sun, Mar, 2, 3600};    // Daylight time = UTC/GMT -4 hours
struct dstRule EndRule = {"EST", First, Sun, Nov, 2, 0};          // Standard time = UTC/GMT -5 hour

Intialize a global instance of the library

// Setup simpleDSTadjust Library rules
simpleDSTadjust dstAdjusted(StartRule, EndRule);

In your code replace your call to time() with the simpleDSTadjust class version of the function.

Minimal version:

time_t t = dstAdjusted.time(NULL);

Version to get the DST adjusted timezone abbreviation

char *dstAbbrev;
time_t t = dstAdjusted.time(&dstAbbrev);

Documentation

Methods

simpleDSTadjust constructor

simpleDSTadjust(struct dstRule startRule, struct dstRule endRule )

initializes the class with the dstRules.

time

time_t time(char **abbrev)

Returns the DST adjusted time in seconds since Jan 1 1970. This is the same functionality as the built-in time() function. However the simpleDSTadjust class version of time() has a char pointer argument instead of a time_t pointer. This is intended for obtaining the timezone abbreviation string. If the argument passed is NULL, there is no difference in functionality other than the DST adjustment.