Merge remote-tracking branch 'upstream/fix-strftime-tz-designation' into integration

# Conflicts:
#	esphome/components/time/posix_tz.cpp
#	esphome/components/time/posix_tz.h

esphome/components/time/posix_tz.cpp

@@ -3,6 +3,8 @@
 #ifdef USE_TIME_TIMEZONE
 
 #include "posix_tz.h"
+#include <cctype>
+#include <cstdio>
 
 namespace esphome::time {
 
@@ -16,6 +18,17 @@ const ParsedTimezone &get_global_tz() { return global_tz_; }
 
 namespace internal {
 
+// Remove before 2026.9.0: parse_uint, skip_tz_name, parse_offset, parse_dst_rule,
+// and parse_transition_time are only used by parse_posix_tz() (bridge code).
+static uint32_t parse_uint(const char *&p) {
+  uint32_t value = 0;
+  while (std::isdigit(static_cast<unsigned char>(*p))) {
+    value = value * 10 + (*p - '0');
+    p++;
+  }
+  return value;
+}
+
 bool is_leap_year(int year) { return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0); }
 
 // Get days in year (avoids duplicate is_leap_year calls)
@@ -109,6 +122,62 @@ void __attribute__((noinline)) epoch_to_tm_utc(time_t epoch, struct tm *out_tm)
   out_tm->tm_isdst = 0;
 }
 
+bool skip_tz_name(const char *&p) {
+  if (*p == '<') {
+    // Angle-bracket quoted name: <+07>, <-03>, <AEST>
+    p++;  // skip '<'
+    while (*p && *p != '>') {
+      p++;
+    }
+    if (*p == '>') {
+      p++;  // skip '>'
+      return true;
+    }
+    return false;  // Unterminated
+  }
+
+  // Standard name: 3+ letters
+  const char *start = p;
+  while (*p && std::isalpha(static_cast<unsigned char>(*p))) {
+    p++;
+  }
+  return (p - start) >= 3;
+}
+
+int32_t __attribute__((noinline)) parse_offset(const char *&p) {
+  int sign = 1;
+  if (*p == '-') {
+    sign = -1;
+    p++;
+  } else if (*p == '+') {
+    p++;
+  }
+
+  int hours = parse_uint(p);
+  int minutes = 0;
+  int seconds = 0;
+
+  if (*p == ':') {
+    p++;
+    minutes = parse_uint(p);
+    if (*p == ':') {
+      p++;
+      seconds = parse_uint(p);
+    }
+  }
+
+  return sign * (hours * 3600 + minutes * 60 + seconds);
+}
+
+// Helper to parse the optional /time suffix (reuses parse_offset logic)
+static void parse_transition_time(const char *&p, DSTRule &rule) {
+  rule.time_seconds = 2 * 3600;  // Default 02:00
+  if (*p == '/') {
+    p++;
+    rule.time_seconds = parse_offset(p);
+  }
+}
+
 void __attribute__((noinline)) julian_to_month_day(int julian_day, int &out_month, int &out_day) {
   // J format: day 1-365, Feb 29 is NOT counted even in leap years
   // So day 60 is always March 1
@@ -149,6 +218,59 @@ void __attribute__((noinline)) day_of_year_to_month_day(int day_of_year, int yea
   out_day = 31;
 }
 
+bool parse_dst_rule(const char *&p, DSTRule &rule) {
+  rule = {};  // Zero initialize
+
+  if (*p == 'M' || *p == 'm') {
+    // M format: Mm.w.d (month.week.day)
+    rule.type = DSTRuleType::MONTH_WEEK_DAY;
+    p++;
+
+    rule.month = parse_uint(p);
+    if (rule.month < 1 || rule.month > 12)
+      return false;
+
+    if (*p++ != '.')
+      return false;
+
+    rule.week = parse_uint(p);
+    if (rule.week < 1 || rule.week > 5)
+      return false;
+
+    if (*p++ != '.')
+      return false;
+
+    rule.day_of_week = parse_uint(p);
+    if (rule.day_of_week > 6)
+      return false;
+
+  } else if (*p == 'J' || *p == 'j') {
+    // J format: Jn (Julian day 1-365, not counting Feb 29)
+    rule.type = DSTRuleType::JULIAN_NO_LEAP;
+    p++;
+
+    rule.day = parse_uint(p);
+    if (rule.day < 1 || rule.day > 365)
+      return false;
+
+  } else if (std::isdigit(static_cast<unsigned char>(*p))) {
+    // Plain number format: n (day 0-365, counting Feb 29)
+    rule.type = DSTRuleType::DAY_OF_YEAR;
+
+    rule.day = parse_uint(p);
+    if (rule.day > 365)
+      return false;
+
+  } else {
+    return false;
+  }
+
+  // Parse optional /time suffix
+  parse_transition_time(p, rule);
+
+  return true;
+}
+
 // Calculate days from Jan 1 of given year to given month/day
 static int __attribute__((noinline)) days_from_year_start(int year, int month, int day) {
   int days = day - 1;
@@ -244,6 +366,95 @@ bool __attribute__((noinline)) is_in_dst(time_t utc_epoch, const ParsedTimezone
   }
 }
 
+// Remove before 2026.9.0: This parser is bridge code for backward compatibility with
+// older Home Assistant clients that send the timezone as a POSIX TZ string instead of
+// the pre-parsed ParsedTimezone protobuf struct. Once all clients send the struct
+// directly, this function and the parsing helpers above (skip_tz_name, parse_offset,
+// parse_dst_rule, parse_transition_time) can be removed.
+// See https://github.com/esphome/backlog/issues/91
+bool parse_posix_tz(const char *tz_string, ParsedTimezone &result) {
+  if (!tz_string || !*tz_string) {
+    return false;
+  }
+
+  const char *p = tz_string;
+
+  // Initialize result (dst_start/dst_end default to type=NONE, so has_dst() returns false)
+  result.std_offset_seconds = 0;
+  result.dst_offset_seconds = 0;
+  result.dst_start = {};
+  result.dst_end = {};
+
+  // Skip standard timezone name
+  if (!internal::skip_tz_name(p)) {
+    return false;
+  }
+
+  // Parse standard offset (required)
+  if (!*p || (!std::isdigit(static_cast<unsigned char>(*p)) && *p != '+' && *p != '-')) {
+    return false;
+  }
+  result.std_offset_seconds = internal::parse_offset(p);
+
+  // Check for DST name
+  if (!*p) {
+    return true;  // No DST
+  }
+
+  // If next char is comma, there's no DST name but there are rules (invalid)
+  if (*p == ',') {
+    return false;
+  }
+
+  // Check if there's something that looks like a DST name start
+  // (letter or angle bracket). If not, treat as trailing garbage and return success.
+  if (!std::isalpha(static_cast<unsigned char>(*p)) && *p != '<') {
+    return true;  // No DST, trailing characters ignored
+  }
+
+  if (!internal::skip_tz_name(p)) {
+    return false;  // Invalid DST name (started but malformed)
+  }
+
+  // Optional DST offset (default is std - 1 hour)
+  if (*p && *p != ',' && (std::isdigit(static_cast<unsigned char>(*p)) || *p == '+' || *p == '-')) {
+    result.dst_offset_seconds = internal::parse_offset(p);
+  } else {
+    result.dst_offset_seconds = result.std_offset_seconds - 3600;
+  }
+
+  // Parse DST rules (required when DST name is present)
+  if (*p != ',') {
+    // DST name without rules - treat as no DST since we can't determine transitions
+    return true;
+  }
+
+  p++;
+  if (!internal::parse_dst_rule(p, result.dst_start)) {
+    return false;
+  }
+
+  // Second rule is required per POSIX
+  if (*p != ',') {
+    return false;
+  }
+  p++;
+  // has_dst() now returns true since dst_start.type was set by parse_dst_rule
+  return internal::parse_dst_rule(p, result.dst_end);
+}
+
+// Format a POSIX offset (positive = west) as "+HHMM" / "-HHMM" for display.
+// Convention: negate POSIX sign so east-of-UTC is positive (ISO 8601 / RFC 2822).
+void format_designation(int32_t posix_offset, char *buf, size_t buf_size) {
+  int32_t display = -posix_offset;
+  char sign = display >= 0 ? '+' : '-';
+  if (display < 0)
+    display = -display;
+  int h = display / 3600;
+  int m = (display % 3600) / 60;
+  snprintf(buf, buf_size, "%c%02d%02d", sign, h, m);
+}
+
 bool epoch_to_local_tm(time_t utc_epoch, const ParsedTimezone &tz, struct tm *out_tm) {
   if (!out_tm) {
     return false;

esphome/components/time/posix_tz.h

@@ -36,6 +36,31 @@ struct ParsedTimezone {
   bool has_dst() const { return this->dst_start.type != DSTRuleType::NONE; }
 };
 
+/// Format a POSIX offset as "+HHMM"/"-HHMM" into buf (must be >= 6 bytes).
+void format_designation(int32_t posix_offset, char *buf, size_t buf_size);
+
+/// Parse a POSIX TZ string into a ParsedTimezone struct.
+///
+/// @deprecated Remove before 2026.9.0 (bridge code for backward compatibility).
+/// This parser only exists so that older Home Assistant clients that send the timezone
+/// as a string (instead of the pre-parsed ParsedTimezone protobuf struct) can still
+/// set the timezone on the device. Once all clients are updated to send the struct
+/// directly, this function and all internal parsing helpers will be removed.
+/// See https://github.com/esphome/backlog/issues/91
+///
+/// Supports formats like:
+///   - "EST5" (simple offset, no DST)
+///   - "EST5EDT,M3.2.0,M11.1.0" (with DST, M-format rules)
+///   - "CST6CDT,M3.2.0/2,M11.1.0/2" (with transition times)
+///   - "<+07>-7" (angle-bracket notation for special names)
+///   - "IST-5:30" (half-hour offsets)
+///   - "EST5EDT,J60,J300" (J-format: Julian day without leap day)
+///   - "EST5EDT,60,300" (plain day number: day of year with leap day)
+/// @param tz_string The POSIX TZ string to parse
+/// @param result Output: the parsed timezone data
+/// @return true if parsing succeeded, false on error
+bool parse_posix_tz(const char *tz_string, ParsedTimezone &result);
+
 /// Convert a UTC epoch to local time using the parsed timezone.
 /// This replaces libc's localtime() to avoid scanf dependency.
 /// @param utc_epoch Unix timestamp in UTC
@@ -59,9 +84,29 @@ const ParsedTimezone &get_global_tz();
 bool is_in_dst(time_t utc_epoch, const ParsedTimezone &tz);
 
 // Internal helper functions exposed for testing.
+// Remove before 2026.9.0: skip_tz_name, parse_offset, parse_dst_rule are only
+// used by parse_posix_tz() which is bridge code for backward compatibility.
+// The remaining helpers (epoch_to_tm_utc, day_of_week, days_in_month, etc.)
+// are used by the conversion functions and will stay.
 
 namespace internal {
 
+/// Skip a timezone name (letters or <...> quoted format)
+/// @param p Pointer to current position, updated on return
+/// @return true if a valid name was found
+bool skip_tz_name(const char *&p);
+
+/// Parse an offset in format [-]hh[:mm[:ss]]
+/// @param p Pointer to current position, updated on return
+/// @return Offset in seconds
+int32_t parse_offset(const char *&p);
+
+/// Parse a DST rule in format Mm.w.d[/time], Jn[/time], or n[/time]
+/// @param p Pointer to current position, updated on return
+/// @param rule Output: the parsed rule
+/// @return true if parsing succeeded
+bool parse_dst_rule(const char *&p, DSTRule &rule);
+
 /// Convert Julian day (J format, 1-365 not counting Feb 29) to month/day
 /// @param julian_day Day number 1-365
 /// @param[out] month Output: month 1-12

esphome/core/time.cpp

@@ -2,6 +2,9 @@
 #include "helpers.h"
 
 #include <algorithm>
+#ifdef USE_TIME_TIMEZONE
+#include "esphome/components/time/posix_tz.h"
+#endif
 
 namespace esphome {
 
@@ -14,12 +17,59 @@ uint8_t days_in_month(uint8_t month, uint16_t year) {
 
 size_t ESPTime::strftime(char *buffer, size_t buffer_len, const char *format) {
   struct tm c_tm = this->to_c_tm();
+#ifdef USE_TIME_TIMEZONE
+  // ::strftime uses libc's internal timezone state for %Z and %z, but we
+  // eliminated setenv("TZ")/tzset() on embedded platforms to save flash.
+  // Substitute %Z and %z with correct values from our parsed timezone.
+  // Quick scan: does format contain %Z or %z (but not %%Z/%%z)?
+  bool needs_subst = false;
+  for (const char *p = format; *p; p++) {
+    if (*p == '%' && *(p + 1)) {
+      p++;
+      if (*p == '%')
+        continue;  // %% is a literal %, skip
+      if (*p == 'Z' || *p == 'z') {
+        needs_subst = true;
+        break;
+      }
+    }
+  }
+  if (needs_subst) {
+    const auto &tz = time::get_global_tz();
+    char designation[6];  // "+HHMM" + null
+    int32_t offset = c_tm.tm_isdst > 0 ? tz.dst_offset_seconds : tz.std_offset_seconds;
+    time::format_designation(offset, designation, sizeof(designation));
+
+    char modified[STRFTIME_BUFFER_SIZE];
+    char *out = modified;
+    char *out_end = modified + sizeof(modified) - 1;
+    for (const char *p = format; *p && out < out_end; p++) {
+      if (*p == '%') {
+        if (*(p + 1) == '%') {
+          // %% → copy both percent signs (literal %)
+          *out++ = *p++;
+          if (out < out_end)
+            *out++ = *p;
+        } else if (*(p + 1) == 'Z' || *(p + 1) == 'z') {
+          p++;  // skip the Z/z
+          for (const char *d = designation; *d && out < out_end; d++)
+            *out++ = *d;
+        } else {
+          *out++ = *p;
+        }
+      } else {
+        *out++ = *p;
+      }
+    }
+    *out = '\0';
+    return ::strftime(buffer, buffer_len, modified, &c_tm);
+  }
+#endif
   return ::strftime(buffer, buffer_len, format, &c_tm);
 }
 
 size_t ESPTime::strftime_to(std::span<char, STRFTIME_BUFFER_SIZE> buffer, const char *format) {
-  struct tm c_tm = this->to_c_tm();
-  size_t len = ::strftime(buffer.data(), buffer.size(), format, &c_tm);
+  size_t len = this->strftime(buffer.data(), buffer.size(), format);
   if (len > 0) {
     return len;
   }