diff --git a/esphome/components/time/posix_tz.cpp b/esphome/components/time/posix_tz.cpp
index 315216b09c..bbceb057a0 100644
--- a/esphome/components/time/posix_tz.cpp
+++ b/esphome/components/time/posix_tz.cpp
@@ -327,18 +327,20 @@ time_t __attribute__((noinline)) calculate_dst_transition(int year, const DSTRul
   return days * 86400 + rule.time_seconds + base_offset_seconds;
 }
 
+}  // namespace internal
+
 bool __attribute__((noinline)) is_in_dst(time_t utc_epoch, const ParsedTimezone &tz) {
   if (!tz.has_dst) {
     return false;
   }
 
-  int year = epoch_to_year(utc_epoch);
+  int year = internal::epoch_to_year(utc_epoch);
 
   // Calculate DST start and end for this year
   // DST start transition happens in standard time
-  time_t dst_start = calculate_dst_transition(year, tz.dst_start, tz.std_offset_seconds);
+  time_t dst_start = internal::calculate_dst_transition(year, tz.dst_start, tz.std_offset_seconds);
   // DST end transition happens in daylight time
-  time_t dst_end = calculate_dst_transition(year, tz.dst_end, tz.dst_offset_seconds);
+  time_t dst_end = internal::calculate_dst_transition(year, tz.dst_end, tz.dst_offset_seconds);
 
   if (dst_start < dst_end) {
     // Northern hemisphere: DST is between start and end
@@ -349,8 +351,6 @@ bool __attribute__((noinline)) is_in_dst(time_t utc_epoch, const ParsedTimezone
   }
 }
 
-}  // namespace internal
-
 bool parse_posix_tz(const char *tz_string, ParsedTimezone &result) {
   if (!tz_string || !*tz_string) {
     return false;
@@ -435,7 +435,7 @@ bool epoch_to_local_tm(time_t utc_epoch, const ParsedTimezone &tz, struct tm *ou
   }
 
   // Determine DST status once (avoids duplicate is_in_dst calculation)
-  bool in_dst = internal::is_in_dst(utc_epoch, tz);
+  bool in_dst = is_in_dst(utc_epoch, tz);
   int32_t offset = in_dst ? tz.dst_offset_seconds : tz.std_offset_seconds;
 
   // Apply offset (POSIX offset is positive west, so subtract to get local)
diff --git a/esphome/components/time/posix_tz.h b/esphome/components/time/posix_tz.h
index 27e51e7519..d44c611fe8 100644
--- a/esphome/components/time/posix_tz.h
+++ b/esphome/components/time/posix_tz.h
@@ -61,6 +61,12 @@ void set_global_tz(const ParsedTimezone &tz);
 /// Get the global timezone.
 const ParsedTimezone &get_global_tz();
 
+/// Check if a given UTC epoch falls within DST for the parsed timezone.
+/// @param utc_epoch Unix timestamp in UTC
+/// @param tz The parsed timezone
+/// @return true if DST is in effect at the given time
+bool is_in_dst(time_t utc_epoch, const ParsedTimezone &tz);
+
 // Internal helper functions exposed for testing
 
 namespace internal {
@@ -114,12 +120,6 @@ void epoch_to_tm_utc(time_t epoch, struct tm *out_tm);
 /// @return Unix epoch timestamp of the transition
 time_t calculate_dst_transition(int year, const DSTRule &rule, int32_t base_offset_seconds);
 
-/// Check if a given UTC epoch falls within DST for the parsed timezone.
-/// @param utc_epoch Unix timestamp in UTC
-/// @param tz The parsed timezone
-/// @return true if DST is in effect at the given time
-bool is_in_dst(time_t utc_epoch, const ParsedTimezone &tz);
-
 }  // namespace internal
 
 }  // namespace esphome::time
diff --git a/esphome/core/time.cpp b/esphome/core/time.cpp
index 918c3c1ffb..aa8dba4b6f 100644
--- a/esphome/core/time.cpp
+++ b/esphome/core/time.cpp
@@ -272,7 +272,7 @@ void ESPTime::recalc_timestamp_local() {
   time_t approx_utc = this->timestamp + tz.std_offset_seconds;
 
   // Check if DST is in effect and apply the appropriate offset
-  if (time::internal::is_in_dst(approx_utc, tz)) {
+  if (time::is_in_dst(approx_utc, tz)) {
     this->timestamp += tz.dst_offset_seconds;
   } else {
     this->timestamp += tz.std_offset_seconds;
@@ -289,7 +289,7 @@ int32_t ESPTime::timezone_offset() {
   const auto &tz = time::get_global_tz();
   // POSIX offset is positive west, but we return offset to add to UTC to get local
   // So we negate the POSIX offset
-  if (time::internal::is_in_dst(now, tz)) {
+  if (time::is_in_dst(now, tz)) {
     return -tz.dst_offset_seconds;
   }
   return -tz.std_offset_seconds;