diff --git a/esphome/components/time/posix_tz.cpp b/esphome/components/time/posix_tz.cpp
index bbceb057a0..1de3504072 100644
--- a/esphome/components/time/posix_tz.cpp
+++ b/esphome/components/time/posix_tz.cpp
@@ -274,6 +274,8 @@ static int __attribute__((noinline)) days_from_year_start(int year, int month, i
 }
 
 // Calculate days from epoch to Jan 1 of given year
+// Note: Only valid for years >= 1970. Pre-1970 timestamps are not supported
+// as they are extremely rare for IoT devices.
 static int64_t __attribute__((noinline)) days_to_year_start(int year) {
   int64_t days = 0;
   for (int y = 1970; y < year; y++) {
diff --git a/esphome/core/time.cpp b/esphome/core/time.cpp
index aa8dba4b6f..e59c33dc23 100644
--- a/esphome/core/time.cpp
+++ b/esphome/core/time.cpp
@@ -86,6 +86,12 @@ static bool expect_char(const char *&p, const char *end, char expected) {
   return true;
 }
 
+// Helper to skip trailing whitespace (for backward compatibility with sscanf)
+static void skip_trailing_whitespace(const char *&p, const char *end) {
+  while (p < end && (*p == ' ' || *p == '\t' || *p == '\n' || *p == '\r'))
+    p++;
+}
+
 bool ESPTime::strptime(const char *time_to_parse, size_t len, ESPTime &esp_time) {
   // Supported formats:
   //   YYYY-MM-DD HH:MM:SS (19 chars)
@@ -150,6 +156,7 @@ bool ESPTime::strptime(const char *time_to_parse, size_t len, ESPTime &esp_time)
       return false;
 
     esp_time.second = v6;
+    skip_trailing_whitespace(p, end);
     return p == end;  // YYYY-MM-DD HH:MM:SS
   }
 
@@ -177,6 +184,7 @@ bool ESPTime::strptime(const char *time_to_parse, size_t len, ESPTime &esp_time)
       return false;
 
     esp_time.second = v3;
+    skip_trailing_whitespace(p, end);
     return p == end;  // HH:MM:SS
   }
 
diff --git a/tests/components/time/posix_tz_parser.cpp b/tests/components/time/posix_tz_parser.cpp
index 4a276d7b71..320eec821a 100644
--- a/tests/components/time/posix_tz_parser.cpp
+++ b/tests/components/time/posix_tz_parser.cpp
@@ -421,13 +421,12 @@ TEST(PosixTzParser, PlainDay365LeapYear) {
   EXPECT_EQ(day, 31);
 }
 
-TEST(PosixTzParser, PlainDay365NonLeapYear) {
-  // Day 365 in non-leap year would be Jan 1 of next year (out of range)
-  // But our function should handle it gracefully
+TEST(PosixTzParser, PlainDay364NonLeapYear) {
+  // Day 364 (0-indexed) is Dec 31 in non-leap year (last valid day)
   int month, day;
   internal::day_of_year_to_month_day(364, 2025, month, day);
   EXPECT_EQ(month, 12);
-  EXPECT_EQ(day, 31);  // Day 364 is Dec 31 in non-leap year
+  EXPECT_EQ(day, 31);
 }
 
 // ============================================================================