See https://github.com/esp8266/Arduino/blob/master/libraries/esp8266/examples/NTP-TZ-DST/
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.
- see https://en.wikipedia.org/wiki/Daylight_saving_time_by_country for details and exceptions
- see http://www.timeanddate.com/time/zones/ for standard abbreviations and additional information
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
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.
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.
See the WeatherStationDemoExtendedDST example for a full implementation including selectable locales, 12/24 hour clock formats and more.
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 hourIntialize 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);simpleDSTadjust(struct dstRule startRule, struct dstRule endRule )
initializes the class with the dstRules.
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.