Add support for time zones

The time zone can be set through the configuration message and applies to all files recorded. File headers contain the UTC time of recording as well as the configured time zone.

main.c

@@ -134,21 +134,31 @@ void setHeaderDetails(uint32_t sampleRate, uint32_t numberOfSamples) {
 
 }
 
-void setHeaderComment(uint32_t currentTime, uint8_t *serialNumber, uint32_t gain) {
+void setHeaderComment(uint32_t currentTime, int8_t timezone, uint8_t *serialNumber, uint32_t gain) {
 
-    time_t rawtime = currentTime;
+    time_t rawtime = currentTime + timezone * SECONDS_IN_HOUR;
 
     struct tm *time = gmtime(&rawtime);
 
     char *comment = wavHeader.icmt.comment;
 
     AM_batteryState_t batteryState = AudioMoth_getBatteryState();
 
-    sprintf(comment, "Recorded at %02d:%02d:%02d %02d/%02d/%04d (UTC) by AudioMoth %08X%08X at gain setting %d while battery state was ",
-            time->tm_hour, time->tm_min, time->tm_sec, time->tm_mday, 1 + time->tm_mon, 1900 + time->tm_year,
-            (unsigned int)*((uint32_t*)serialNumber + 1), (unsigned int)*((uint32_t*)serialNumber), (unsigned int)gain);
+    sprintf(comment, "Recorded at %02d:%02d:%02d %02d/%02d/%04d (UTC", time->tm_hour, time->tm_min, time->tm_sec, time->tm_mday, 1 + time->tm_mon, 1900 + time->tm_year);
+
+    comment += 36;
+
+    if (timezone < 0) sprintf(comment, "%d", timezone);
+
+    if (timezone > 0) sprintf(comment, "+%d", timezone);
 
-    comment += 110;
+    if (timezone < 0 || timezone > 0) comment += 2;
+
+    if (timezone < -9 || timezone > 9) comment += 1;
+
+    sprintf(comment, ") by AudioMoth %08X%08X at gain setting %d while battery state was ", (unsigned int)*((uint32_t*)serialNumber + 1), (unsigned int)*((uint32_t*)serialNumber), (unsigned int)gain);
+
+    comment += 74;
 
     if (batteryState == AM_BATTERY_LOW) {
 
@@ -190,6 +200,7 @@ typedef struct {
     uint8_t enableLED;
     uint8_t activeStartStopPeriods;
     startStopPeriod_t startStopPeriods[MAX_START_STOP_PERIODS];
+    int8_t timezone;
 } configSettings_t;
 
 #pragma pack(pop)
@@ -212,7 +223,8 @@ configSettings_t defaultConfigSettings = {
         {.startMinutes = 540, .stopMinutes = 600},
         {.startMinutes = 720, .stopMinutes = 780},
         {.startMinutes = 900, .stopMinutes = 960}
-    }
+    },
+    .timezone = 0
 };
 
 uint32_t *previousSwitchPosition = (uint32_t*)AM_BACKUP_DOMAIN_START_ADDRESS;
@@ -387,6 +399,15 @@ int main(void) {
 
 }
 
+/* Time zone handler */
+
+void AudioMoth_timezoneRequested(int8_t *timezone) {
+
+    *timezone = configSettings->timezone;
+
+}
+
+
 /* AudioMoth interrupt handlers */
 
 inline void AudioMoth_handleSwitchInterrupt() {
@@ -583,9 +604,9 @@ static void makeRecording(uint32_t currentTime, uint32_t recordDuration, bool en
 
     RETURN_ON_ERROR(AudioMoth_enableFileSystem());
 
-    /* Open a file with the name as a UNIX time stamp in HEX */
+    /* Open a file with the current local time as the name */
 
-    time_t rawtime = currentTime;
+    time_t rawtime = currentTime + configSettings->timezone * SECONDS_IN_HOUR;
 
     struct tm *time = gmtime(&rawtime);
 
@@ -653,7 +674,7 @@ static void makeRecording(uint32_t currentTime, uint32_t recordDuration, bool en
 
     setHeaderDetails(configSettings->sampleRate / configSettings->sampleRateDivider, samplesWritten - numberOfSamplesInHeader);
 
-    setHeaderComment(currentTime, (uint8_t*)AM_UNIQUE_ID_START_ADDRESS, configSettings->gain);
+    setHeaderComment(currentTime, configSettings->timezone, (uint8_t*)AM_UNIQUE_ID_START_ADDRESS, configSettings->gain);
 
     /* Write the header */