Parse build.time as an ISO 8601 instant

Closes gh-12420

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/info/BuildProperties.java

@@ -16,9 +16,9 @@
 
 package org.springframework.boot.info;
 
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
+import java.time.DateTimeException;
 import java.time.Instant;
+import java.time.format.DateTimeFormatter;
 import java.util.Properties;
 
 /**
@@ -89,12 +89,12 @@ public class BuildProperties extends InfoProperties {
 	private static void coerceDate(Properties properties, String key) {
 		String value = properties.getProperty(key);
 		if (value != null) {
-			SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");
 			try {
-				String updatedValue = String.valueOf(format.parse(value).getTime());
+				String updatedValue = String.valueOf(DateTimeFormatter.ISO_INSTANT
+						.parse(value, Instant::from).toEpochMilli());
 				properties.setProperty(key, updatedValue);
 			}
-			catch (ParseException ex) {
+			catch (DateTimeException ex) {
 				// Ignore and store the original value
 			}
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/info/BuildPropertiesTests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.info;
 
+import java.time.Instant;
+import java.time.format.DateTimeFormatter;
 import java.util.Properties;
 
 import org.junit.Test;
@@ -31,14 +33,15 @@ public class BuildPropertiesTests {
 
 	@Test
 	public void basicInfo() {
+		Instant instant = Instant.now();
 		BuildProperties properties = new BuildProperties(createProperties("com.example",
-				"demo", "0.0.1", "2016-03-04T14:36:33+0100"));
+				"demo", "0.0.1", DateTimeFormatter.ISO_INSTANT.format(instant)));
 		assertThat(properties.getGroup()).isEqualTo("com.example");
 		assertThat(properties.getArtifact()).isEqualTo("demo");
 		assertThat(properties.getVersion()).isEqualTo("0.0.1");
-		assertThat(properties.getTime()).isNotNull();
-		assertThat(properties.get("time")).isEqualTo("1457098593000");
-		assertThat(properties.getTime().toEpochMilli()).isEqualTo(1457098593000L);
+		assertThat(properties.getTime()).isEqualTo(instant);
+		assertThat(properties.get("time"))
+				.isEqualTo(String.valueOf(instant.toEpochMilli()));
 	}
 
 	@Test