Change build_time_str format to ISO 8601 with timezone

Use YYYY-MM-DD HH:MM:SS +ZZZZ format instead of the locale-dependent
'%b %d %Y, %H:%M:%S' format. This provides:
- Unambiguous date format (YYYY-MM-DD)
- Timezone information
- Locale-independent formatting
- Better sortability and parseability

Example: "2025-12-15 16:30:27 +0000" instead of "Dec 15 2025, 16:30:27"

Tests validate the format using strptime with '%Y-%m-%d %H:%M:%S %z'.

esphome/writer.py

@@ -340,7 +340,7 @@ def get_build_info() -> tuple[int, int, str]:
     """
     config_hash = CORE.config_hash
     build_time = int(time.time())
-    build_time_str = time.strftime("%b %d %Y, %H:%M:%S", time.localtime(build_time))
+    build_time_str = time.strftime("%Y-%m-%d %H:%M:%S %z", time.localtime(build_time))
     return config_hash, build_time, build_time_str
 
 

tests/integration/test_build_info.py

@@ -30,8 +30,8 @@ async def test_build_info(
         compilation_time = device_info.compilation_time
         assert compilation_time is not None
 
-        # Parse the date string - raises ValueError if format is wrong
-        parsed = datetime.strptime(compilation_time, "%b %d %Y, %H:%M:%S")
+        # Validate the ISO format: "YYYY-MM-DD HH:MM:SS +ZZZZ"
+        parsed = datetime.strptime(compilation_time, "%Y-%m-%d %H:%M:%S %z")
         assert parsed.year >= time.localtime().tm_year
 
         # Get entities
@@ -98,13 +98,14 @@ async def test_build_info(
             f"build_time {build_time} should be within the last hour"
         )
 
-        # Validate build_time_str matches the same format as compilation_time
+        # Validate build_time_str matches the new ISO format
         build_time_str = build_time_str_state.state
-        parsed_build_time = datetime.strptime(build_time_str, "%b %d %Y, %H:%M:%S")
+        # Format: "YYYY-MM-DD HH:MM:SS +ZZZZ"
+        parsed_build_time = datetime.strptime(build_time_str, "%Y-%m-%d %H:%M:%S %z")
         assert parsed_build_time.year >= time.localtime().tm_year
 
         # Verify build_time_str matches what we get from build_time timestamp
-        expected_str = time.strftime("%b %d %Y, %H:%M:%S", time.localtime(build_time))
+        expected_str = time.strftime("%Y-%m-%d %H:%M:%S %z", time.localtime(build_time))
         assert build_time_str == expected_str, (
             f"build_time_str '{build_time_str}' should match timestamp '{expected_str}'"
         )

tests/unit_tests/test_writer.py

@@ -1194,7 +1194,7 @@ def test_get_build_info_new_build(
     assert build_time > 0
     assert isinstance(build_time_str, str)
     # Verify build_time_str format matches expected pattern
-    assert len(build_time_str) > 10  # e.g., "Dec 13 2025, 12:00:00"
+    assert len(build_time_str) >= 19  # e.g., "2025-12-15 16:27:44 +0000"
 
 
 @patch("esphome.writer.CORE")
@@ -1209,7 +1209,7 @@ def test_get_build_info_always_returns_current_time(
 
     # Create existing build_info.json with matching config_hash and version
     existing_build_time = 1700000000
-    existing_build_time_str = "Nov 14 2023, 22:13:20"
+    existing_build_time_str = "2023-11-14 22:13:20 +0000"
     build_info_path.write_text(
         json.dumps(
             {
@@ -1248,7 +1248,7 @@ def test_get_build_info_config_changed(
             {
                 "config_hash": 0x12345678,  # Different
                 "build_time": existing_build_time,
-                "build_time_str": "Nov 14 2023, 22:13:20",
+                "build_time_str": "2023-11-14 22:13:20 +0000",
                 "esphome_version": "2025.1.0-dev",
             }
         )
@@ -1279,7 +1279,7 @@ def test_get_build_info_version_changed(
             {
                 "config_hash": 0x12345678,
                 "build_time": existing_build_time,
-                "build_time_str": "Nov 14 2023, 22:13:20",
+                "build_time_str": "2023-11-14 22:13:20 +0000",
                 "esphome_version": "2024.12.0",  # Old version
             }
         )
@@ -1346,8 +1346,9 @@ def test_get_build_info_build_time_str_format(
 
     config_hash, build_time, build_time_str = get_build_info()
 
-    # Verify the format matches "%b %d %Y, %H:%M:%S" (e.g., "Dec 13 2025, 14:30:45")
-    parsed = datetime.strptime(build_time_str, "%b %d %Y, %H:%M:%S")
+    # Verify the format matches "%Y-%m-%d %H:%M:%S %z"
+    # e.g., "2025-12-15 16:27:44 +0000"
+    parsed = datetime.strptime(build_time_str, "%Y-%m-%d %H:%M:%S %z")
     assert parsed.year >= 2024
 
 
@@ -1355,14 +1356,14 @@ def test_generate_build_info_data_h_format() -> None:
     """Test generate_build_info_data_h produces correct header content."""
     config_hash = 0x12345678
     build_time = 1700000000
-    build_time_str = "Nov 14 2023, 22:13:20"
+    build_time_str = "2023-11-14 22:13:20 +0000"
 
     result = generate_build_info_data_h(config_hash, build_time, build_time_str)
 
     assert "#pragma once" in result
     assert "#define ESPHOME_CONFIG_HASH 0x12345678U" in result
     assert "#define ESPHOME_BUILD_TIME 1700000000" in result
-    assert 'ESPHOME_BUILD_TIME_STR[] = "Nov 14 2023, 22:13:20"' in result
+    assert 'ESPHOME_BUILD_TIME_STR[] = "2023-11-14 22:13:20 +0000"' in result
 
 
 def test_generate_build_info_data_h_esp8266_progmem() -> None: