diff --git a/spring-context/src/main/java/org/springframework/format/datetime/standard/InstantFormatter.java b/spring-context/src/main/java/org/springframework/format/datetime/standard/InstantFormatter.java
index 985006e3ba388203ba002e0db72927ba0b1940c0..010d004ae5d74267ce607065533d3782a7b8e182 100644
--- a/spring-context/src/main/java/org/springframework/format/datetime/standard/InstantFormatter.java
+++ b/spring-context/src/main/java/org/springframework/format/datetime/standard/InstantFormatter.java
@@ -40,14 +40,14 @@ public class InstantFormatter implements Formatter<Instant> {
 
 	@Override
 	public Instant parse(String text, Locale locale) throws ParseException {
-		if (text.length() > 0 && Character.isDigit(text.charAt(0))) {
-			// assuming UTC instant a la "2007-12-03T10:15:30.00Z"
-			return Instant.parse(text);
-		}
-		else {
+		if (text.length() > 0 && Character.isAlphabetic(text.charAt(0))) {
 			// assuming RFC-1123 value a la "Tue, 3 Jun 2008 11:05:30 GMT"
 			return Instant.from(DateTimeFormatter.RFC_1123_DATE_TIME.parse(text));
 		}
+		else {
+			// assuming UTC instant a la "2007-12-03T10:15:30.00Z"
+			return Instant.parse(text);
+		}
 	}
 
 	@Override
diff --git a/spring-context/src/test/java/org/springframework/format/datetime/standard/InstantFormatterTests.java b/spring-context/src/test/java/org/springframework/format/datetime/standard/InstantFormatterTests.java
new file mode 100644
index 0000000000000000000000000000000000000000..5e9b0814fcbd78f5e72efd5f2546b3ff9ae163a5
--- /dev/null
+++ b/spring-context/src/test/java/org/springframework/format/datetime/standard/InstantFormatterTests.java
@@ -0,0 +1,119 @@
+/*
+ * Copyright 2002-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.format.datetime.standard;
+
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+
+import java.text.ParseException;
+import java.time.Instant;
+import java.time.format.DateTimeFormatter;
+import java.util.Random;
+import java.util.stream.Stream;
+
+import static java.time.Instant.MAX;
+import static java.time.Instant.MIN;
+import static java.time.ZoneId.systemDefault;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Andrei Nevedomskii
+ */
+@SuppressWarnings("ConstantConditions")
+class InstantFormatterTests {
+
+	private final InstantFormatter instantFormatter = new InstantFormatter();
+
+	@ParameterizedTest
+	@ArgumentsSource(ISOSerializedInstantProvider.class)
+	void should_parse_an_ISO_formatted_string_representation_of_an_instant(String input) throws ParseException {
+		Instant expected = DateTimeFormatter.ISO_INSTANT.parse(input, Instant::from);
+
+		Instant actual = instantFormatter.parse(input, null);
+
+		assertThat(actual).isEqualTo(expected);
+	}
+
+	@ParameterizedTest
+	@ArgumentsSource(RFC1123SerializedInstantProvider.class)
+	void should_parse_an_RFC1123_formatted_string_representation_of_an_instant(String input) throws ParseException {
+		Instant expected = DateTimeFormatter.RFC_1123_DATE_TIME.parse(input, Instant::from);
+
+		Instant actual = instantFormatter.parse(input, null);
+
+		assertThat(actual).isEqualTo(expected);
+	}
+
+	@ParameterizedTest
+	@ArgumentsSource(RandomInstantProvider.class)
+	void should_serialize_an_instant_using_ISO_format_and_ignoring_locale(Instant input) {
+		String expected = DateTimeFormatter.ISO_INSTANT.format(input);
+
+		String actual = instantFormatter.print(input, null);
+
+		assertThat(actual).isEqualTo(expected);
+	}
+
+	private static class ISOSerializedInstantProvider extends RandomInstantProvider {
+
+		@Override
+		Stream<?> provideArguments() {
+			return randomInstantStream(MIN, MAX).map(DateTimeFormatter.ISO_INSTANT::format);
+		}
+	}
+
+	private static class RFC1123SerializedInstantProvider extends RandomInstantProvider {
+
+		// RFC-1123 supports only 4-digit years
+		private final Instant min = Instant.parse("0000-01-01T00:00:00.00Z");
+
+		private final Instant max = Instant.parse("9999-12-31T23:59:59.99Z");
+
+		@Override
+		Stream<?> provideArguments() {
+			return randomInstantStream(min, max)
+					.map(DateTimeFormatter.RFC_1123_DATE_TIME.withZone(systemDefault())::format);
+		}
+	}
+
+	private static class RandomInstantProvider implements ArgumentsProvider {
+
+		private static final long DATA_SET_SIZE = 10;
+
+		static final Random RANDOM = new Random();
+
+		Stream<?> provideArguments() {
+			return randomInstantStream(MIN, MAX);
+		}
+
+		@Override
+		public final Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+			return provideArguments().map(Arguments::of).limit(DATA_SET_SIZE);
+		}
+
+		Stream<Instant> randomInstantStream(Instant min, Instant max) {
+			return Stream.concat(
+					Stream.of(Instant.now()), // make sure that the data set includes current instant
+					RANDOM.longs(min.getEpochSecond(), max.getEpochSecond())
+							.mapToObj(Instant::ofEpochSecond)
+			);
+		}
+	}
+}
\ No newline at end of file