Some POSIX time zones are not handled correctly

[rjwats]

Basic Infos

• This issue complies with the issue POLICY doc.
• I have read the documentation at readthedocs and the issue is not addressed there.
• I have tested that the issue is present in current master branch (aka latest git).
• I have searched the issue tracker for a similar issue.
• If there is a stack dump, I have decoded it.
• I have filled out all fields below.

Platform

• Hardware: [ESP-12]
• Core Version: [2.7.4]
• Development Env: [Arduino IDE]
• Operating System: [Windows]

Settings in IDE

• Module: [Generic ESP8266 Module]
• Flash Mode: [dio]
• Flash Size: [4MB]
• lwip Variant: [v2 Lower Memory]
• Reset Method: [nodemcu]
• Flash Frequency: [40Mhz]
• CPU Frequency: [80Mhz]
• Upload Using: [SERIAL]
• Upload Speed: [115200]

Problem Description

It looks as if some POSIX time zone strings may be being interpreted incorrectly when configured using:

configTime(const char* tz, const char* server1, const char* server2, const char* server3)

or

setTZ(const char* tz)

The following examples have been taken from TZ.h:

The following are some of the values which demonstrate the issue:

#define TZ_America_Sao_Paulo	PSTR("<-03>3") // Offset by +03:00 instead of -03:00
#define TZ_Africa_Casablanca	PSTR("<+01>-1") // Offset by -01:00 instead of +01:00
#define TZ_America_Asuncion	PSTR("<-04>4<-03>,M10.1.0/0,M3.4.0/0") // Offset by +4:00 instead of -03:00

This pattern appears consistent for all time zones which are defined in this format.

By contrast the following (also taken from TZ.h) do not exhibit this issue:

#define TZ_America_Los_Angeles	PSTR("PST8PDT,M3.2.0,M11.1.0") // Offset by -08:00
#define TZ_Europe_Rome	PSTR("CET-1CEST,M3.5.0,M10.5.0/3") // Offset by +01:00
#define TZ_Europe_Kaliningrad	PSTR("EET-2") // Offset by +02:00

All of the examples above were tested today @ ~1604351488 unix timestamp.

MCVE Sketch

#ifndef STASSID
#define STASSID "VM723402-2G"
#define STAPSK  "gmwscxnu"
#endif

#include <TZ.h>

#define MYTZ TZ_America_Sao_Paulo

#include <ESP8266WiFi.h>
#include <coredecls.h>
#include <PolledTimeout.h>

#include <time.h>
#include <sys/time.h>

extern "C" int clock_gettime(clockid_t unused, struct timespec *tp);

static time_t now;
static esp8266::polledTimeout::periodicMs showTimeNow(5000);

String toISOString(tm* time) {
  char time_string[25];
  strftime(time_string, 25, "%FT%T", time);
  return String(time_string);
}

void showTime() {
  now = time(nullptr);
  Serial.print("gmtime:     ");
  Serial.println(toISOString(gmtime(&now)));
  Serial.print("localtime:  ");
  Serial.println(toISOString(localtime(&now)));
}

void time_is_set_scheduled() {
  showTime();
}

void setup() {
  Serial.begin(115200);
  Serial.println("Starting...");

  settimeofday_cb(time_is_set_scheduled);

  // Set the timezone
  configTime(MYTZ, "pool.ntp.org");

  // start network
  WiFi.persistent(false);
  WiFi.mode(WIFI_STA);
  WiFi.begin(STASSID, STAPSK);
}

void loop() {
  if (showTimeNow) {
    showTime();
  }
}

Debug Messages

One example, when using TZ_America_Sao_Paulo, local time should be offset -03:00, instead it is offset +03:00:

gmtime:     2020-11-02T20:36:51
localtime:  2020-11-02T23:36:51
gmtime:     2020-11-02T20:36:56
localtime:  2020-11-02T23:36:56
gmtime:     2020-11-02T20:37:01
localtime:  2020-11-02T23:37:01
gmtime:     2020-11-02T20:37:06
localtime:  2020-11-02T23:37:06

[d-a-v]

Thanks for the report and MCVE.
This is reproducible.
I don't think it could be on newlib but we are using their API and we make no difference from working TZ and Sao Paulo.
I have so far no idea where it comes from.

[d-a-v]

This is fixed by #7699

[rjwats]

Nice, thanks 👍