From 54a4d60f5d26fc6a04ae18a82bf2b52e84d65f9e Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Sun, 18 Jan 2026 23:09:24 -1000
Subject: [PATCH] [datetime] Add const char * overloads for string parsing to
 avoid heap allocation

---
 esphome/components/datetime/date_entity.cpp     | 4 ++--
 esphome/components/datetime/date_entity.h       | 5 +++--
 esphome/components/datetime/datetime_entity.cpp | 4 ++--
 esphome/components/datetime/datetime_entity.h   | 7 +++++--
 esphome/components/datetime/time_entity.cpp     | 4 ++--
 esphome/components/datetime/time_entity.h       | 5 +++--
 6 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/esphome/components/datetime/date_entity.cpp b/esphome/components/datetime/date_entity.cpp
index c0851a9f9f..3ba488c0aa 100644
--- a/esphome/components/datetime/date_entity.cpp
+++ b/esphome/components/datetime/date_entity.cpp
@@ -106,9 +106,9 @@ DateCall &DateCall::set_date(uint16_t year, uint8_t month, uint8_t day) {
 
 DateCall &DateCall::set_date(ESPTime time) { return this->set_date(time.year, time.month, time.day_of_month); };
 
-DateCall &DateCall::set_date(const char *date) {
+DateCall &DateCall::set_date(const char *date, size_t len) {
   ESPTime val{};
-  if (!ESPTime::strptime(date, val)) {
+  if (!ESPTime::strptime(date, len, val)) {
     ESP_LOGE(TAG, "Could not convert the date string to an ESPTime object");
     return *this;
   }
diff --git a/esphome/components/datetime/date_entity.h b/esphome/components/datetime/date_entity.h
index 60aca059a9..955fd92c45 100644
--- a/esphome/components/datetime/date_entity.h
+++ b/esphome/components/datetime/date_entity.h
@@ -67,8 +67,9 @@ class DateCall {
   void perform();
   DateCall &set_date(uint16_t year, uint8_t month, uint8_t day);
   DateCall &set_date(ESPTime time);
-  DateCall &set_date(const char *date);
-  DateCall &set_date(const std::string &date) { return this->set_date(date.c_str()); }
+  DateCall &set_date(const char *date, size_t len);
+  DateCall &set_date(const char *date) { return this->set_date(date, strlen(date)); }
+  DateCall &set_date(const std::string &date) { return this->set_date(date.c_str(), date.size()); }
 
   DateCall &set_year(uint16_t year) {
     this->year_ = year;
diff --git a/esphome/components/datetime/datetime_entity.cpp b/esphome/components/datetime/datetime_entity.cpp
index 67eaf3f78e..730abb3ca8 100644
--- a/esphome/components/datetime/datetime_entity.cpp
+++ b/esphome/components/datetime/datetime_entity.cpp
@@ -163,9 +163,9 @@ DateTimeCall &DateTimeCall::set_datetime(ESPTime datetime) {
                             datetime.second);
 };
 
-DateTimeCall &DateTimeCall::set_datetime(const char *datetime) {
+DateTimeCall &DateTimeCall::set_datetime(const char *datetime, size_t len) {
   ESPTime val{};
-  if (!ESPTime::strptime(datetime, val)) {
+  if (!ESPTime::strptime(datetime, len, val)) {
     ESP_LOGE(TAG, "Could not convert the time string to an ESPTime object");
     return *this;
   }
diff --git a/esphome/components/datetime/datetime_entity.h b/esphome/components/datetime/datetime_entity.h
index 3d8f05217c..b5b8cd677e 100644
--- a/esphome/components/datetime/datetime_entity.h
+++ b/esphome/components/datetime/datetime_entity.h
@@ -71,8 +71,11 @@ class DateTimeCall {
   void perform();
   DateTimeCall &set_datetime(uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second);
   DateTimeCall &set_datetime(ESPTime datetime);
-  DateTimeCall &set_datetime(const char *datetime);
-  DateTimeCall &set_datetime(const std::string &datetime) { return this->set_datetime(datetime.c_str()); }
+  DateTimeCall &set_datetime(const char *datetime, size_t len);
+  DateTimeCall &set_datetime(const char *datetime) { return this->set_datetime(datetime, strlen(datetime)); }
+  DateTimeCall &set_datetime(const std::string &datetime) {
+    return this->set_datetime(datetime.c_str(), datetime.size());
+  }
   DateTimeCall &set_datetime(time_t epoch_seconds);
 
   DateTimeCall &set_year(uint16_t year) {
diff --git a/esphome/components/datetime/time_entity.cpp b/esphome/components/datetime/time_entity.cpp
index f2daa9c0b5..74e43fbbe7 100644
--- a/esphome/components/datetime/time_entity.cpp
+++ b/esphome/components/datetime/time_entity.cpp
@@ -74,9 +74,9 @@ TimeCall &TimeCall::set_time(uint8_t hour, uint8_t minute, uint8_t second) {
 
 TimeCall &TimeCall::set_time(ESPTime time) { return this->set_time(time.hour, time.minute, time.second); };
 
-TimeCall &TimeCall::set_time(const char *time) {
+TimeCall &TimeCall::set_time(const char *time, size_t len) {
   ESPTime val{};
-  if (!ESPTime::strptime(time, val)) {
+  if (!ESPTime::strptime(time, len, val)) {
     ESP_LOGE(TAG, "Could not convert the time string to an ESPTime object");
     return *this;
   }
diff --git a/esphome/components/datetime/time_entity.h b/esphome/components/datetime/time_entity.h
index 8122c95173..e4bb113eb5 100644
--- a/esphome/components/datetime/time_entity.h
+++ b/esphome/components/datetime/time_entity.h
@@ -69,8 +69,9 @@ class TimeCall {
   void perform();
   TimeCall &set_time(uint8_t hour, uint8_t minute, uint8_t second);
   TimeCall &set_time(ESPTime time);
-  TimeCall &set_time(const char *time);
-  TimeCall &set_time(const std::string &time) { return this->set_time(time.c_str()); }
+  TimeCall &set_time(const char *time, size_t len);
+  TimeCall &set_time(const char *time) { return this->set_time(time, strlen(time)); }
+  TimeCall &set_time(const std::string &time) { return this->set_time(time.c_str(), time.size()); }
 
   TimeCall &set_hour(uint8_t hour) {
     this->hour_ = hour;