diff --git a/tests/corelib/date_time4_test.dart b/tests/corelib/date_time4_test.dart
index 4342019f8c67..06a8a3a0465e 100644
--- a/tests/corelib/date_time4_test.dart
+++ b/tests/corelib/date_time4_test.dart
@@ -6,60 +6,7 @@ import "package:expect/expect.dart";
 
 // Test fromString with 6 digits after the decimal point.
 
-bool get supportsMicroseconds =>
-    new DateTime.fromMicrosecondsSinceEpoch(1).microsecondsSinceEpoch == 1;
-
 main() {
-  if (supportsMicroseconds) {
-    testMicrosecondPrecision();
-  } else {
-    testMillisecondPrecision();
-  }
-}
-
-void testMillisecondPrecision() {
-  // We only support milliseconds. If the user supplies more data (the "51"
-  // here), we round.
-  DateTime dt1 = DateTime.parse("1999-01-02 23:59:59.999519");
-  Expect.equals(1999, dt1.year);
-  Expect.equals(1, dt1.month);
-  Expect.equals(3, dt1.day);
-  Expect.equals(0, dt1.hour);
-  Expect.equals(0, dt1.minute);
-  Expect.equals(0, dt1.second);
-  Expect.equals(0, dt1.millisecond);
-  Expect.equals(false, dt1.isUtc);
-  dt1 = DateTime.parse("1999-01-02 23:58:59.999519Z");
-  Expect.equals(1999, dt1.year);
-  Expect.equals(1, dt1.month);
-  Expect.equals(2, dt1.day);
-  Expect.equals(23, dt1.hour);
-  Expect.equals(59, dt1.minute);
-  Expect.equals(0, dt1.second);
-  Expect.equals(0, dt1.millisecond);
-  Expect.equals(true, dt1.isUtc);
-  dt1 = DateTime.parse("0009-09-09 09:09:09.009411Z");
-  Expect.equals(9, dt1.year);
-  Expect.equals(9, dt1.month);
-  Expect.equals(9, dt1.day);
-  Expect.equals(9, dt1.hour);
-  Expect.equals(9, dt1.minute);
-  Expect.equals(9, dt1.second);
-  Expect.equals(9, dt1.millisecond);
-  Expect.equals(true, dt1.isUtc);
-  String svnDate = "2012-03-30T04:28:13.752341Z";
-  dt1 = DateTime.parse(svnDate);
-  Expect.equals(2012, dt1.year);
-  Expect.equals(3, dt1.month);
-  Expect.equals(30, dt1.day);
-  Expect.equals(4, dt1.hour);
-  Expect.equals(28, dt1.minute);
-  Expect.equals(13, dt1.second);
-  Expect.equals(752, dt1.millisecond);
-  Expect.equals(true, dt1.isUtc);
-}
-
-void testMicrosecondPrecision() {
   DateTime dt1 = DateTime.parse("1999-01-02 23:59:59.999519");
   Expect.equals(1999, dt1.year);
   Expect.equals(1, dt1.month);
diff --git a/tests/corelib/date_time_extremes_test.dart b/tests/corelib/date_time_extremes_test.dart
index ad5316fc30b8..329db67eea4e 100644
--- a/tests/corelib/date_time_extremes_test.dart
+++ b/tests/corelib/date_time_extremes_test.dart
@@ -6,9 +6,6 @@ import "package:expect/expect.dart";
 
 // Dart test program for DateTime, extreme values.
 
-bool get supportsMicroseconds =>
-    DateTime.fromMicrosecondsSinceEpoch(1).microsecondsSinceEpoch == 1;
-
 // Identical to _maxMillisecondsSinceEpoch in date_time.dart
 const int _MAX_MILLISECONDS = 8640000000000000;
 
@@ -61,8 +58,6 @@ void testExtremes() {
   Expect.throws(
       () => DateTime.utc(dt.year, dt.month, dt.day, dt.hour, dt.minute, 0, -1));
 
-  if (!supportsMicroseconds) return;
-
   /// The nearest value to [base] in the direction [delta]. For native `int`s,
   /// this is just `base + delta`. For web `int`s outside the safe range, the
   /// next value might differ by some power of two.
diff --git a/tests/corelib/date_time_far_away_dates_test.dart b/tests/corelib/date_time_far_away_dates_test.dart
index 6a810f722a0b..d5ab6bb68ca3 100644
--- a/tests/corelib/date_time_far_away_dates_test.dart
+++ b/tests/corelib/date_time_far_away_dates_test.dart
@@ -9,9 +9,6 @@ import "package:expect/expect.dart";
 // TODO(37442): Find far-away dates with milliseconds-since-epoch values that
 // are 'web' integers.
 
-bool get supportsMicroseconds =>
-    DateTime.fromMicrosecondsSinceEpoch(1).microsecondsSinceEpoch == 1;
-
 void testFarAwayDates() {
   DateTime dt =
       DateTime.fromMillisecondsSinceEpoch(1000000000000001, isUtc: true);
@@ -66,8 +63,6 @@ void testFarAwayDates() {
   Expect.equals(999, dt.millisecond);
   Expect.equals(0, dt.microsecond);
 
-  if (!supportsMicroseconds) return;
-
   // `1000000000000000128` is a valid web number, allowing this test to be
   // compiled by the web compilers.
   dt = DateTime.fromMicrosecondsSinceEpoch(1000000000000000128, isUtc: true);
diff --git a/tests/corelib/date_time_parse_test.dart b/tests/corelib/date_time_parse_test.dart
index 23b8b02ddd17..4fb377b7cc9c 100644
--- a/tests/corelib/date_time_parse_test.dart
+++ b/tests/corelib/date_time_parse_test.dart
@@ -10,22 +10,12 @@ check(DateTime expected, String str) {
   Expect.equals(expected.isUtc, actual.isUtc);
 }
 
-bool get supportsMicroseconds =>
-    new DateTime.fromMicrosecondsSinceEpoch(1).microsecondsSinceEpoch == 1;
-
 main() {
   check(new DateTime(2012, 02, 27, 13, 27), "2012-02-27 13:27:00");
-  if (supportsMicroseconds) {
-    check(new DateTime.utc(2012, 02, 27, 13, 27, 0, 123, 456),
-        "2012-02-27 13:27:00.1234567891234z");
-    check(new DateTime.utc(2012, 02, 27, 13, 27, 0, 123, 456),
-        "2012-02-27 13:27:00,1234567891234z");
-  } else {
-    check(new DateTime.utc(2012, 02, 27, 13, 27, 0, 123, 0),
-        "2012-02-27 13:27:00.1234567891234z");
-    check(new DateTime.utc(2012, 02, 27, 13, 27, 0, 123, 0),
-        "2012-02-27 13:27:00,1234567891234z");
-  }
+  check(new DateTime.utc(2012, 02, 27, 13, 27, 0, 123, 456),
+      "2012-02-27 13:27:00.1234567891234z");
+  check(new DateTime.utc(2012, 02, 27, 13, 27, 0, 123, 456),
+      "2012-02-27 13:27:00,1234567891234z");
   check(new DateTime(2012, 02, 27, 13, 27), "20120227 13:27:00");
   check(new DateTime(2012, 02, 27, 13, 27), "20120227T132700");
   check(new DateTime(2012, 02, 27), "20120227");
@@ -42,15 +32,8 @@ main() {
   check(
       new DateTime.utc(2015, 02, 14, 13, 0, 0, 0), "2015-02-15T00:00:00+11:00");
 
-  if (supportsMicroseconds) {
-    check(new DateTime.utc(2015, 02, 15, 0, 0, 0, 500, 500),
-        "2015-02-15T00:00:00.500500Z");
-    check(new DateTime.utc(2015, 02, 15, 0, 0, 0, 511, 500),
-        "2015-02-15T00:00:00.511500Z");
-  } else {
-    check(new DateTime.utc(2015, 02, 15, 0, 0, 0, 501),
-        "2015-02-15T00:00:00.501Z");
-    check(new DateTime.utc(2015, 02, 15, 0, 0, 0, 512),
-        "2015-02-15T00:00:00.512Z");
-  }
+  check(new DateTime.utc(2015, 02, 15, 0, 0, 0, 500, 500),
+      "2015-02-15T00:00:00.500500Z");
+  check(new DateTime.utc(2015, 02, 15, 0, 0, 0, 511, 500),
+      "2015-02-15T00:00:00.511500Z");
 }
diff --git a/tests/corelib/date_time_test.dart b/tests/corelib/date_time_test.dart
index 63e8136c0f30..08f8323daca1 100644
--- a/tests/corelib/date_time_test.dart
+++ b/tests/corelib/date_time_test.dart
@@ -6,9 +6,6 @@ import "package:expect/expect.dart";
 
 // Dart test program for DateTime.
 
-bool get supportsMicroseconds =>
-    new DateTime.fromMicrosecondsSinceEpoch(1).microsecondsSinceEpoch == 1;
-
 // Identical to _maxMillisecondsSinceEpoch in date_time.dart
 const int _MAX_MILLISECONDS = 8640000000000000;
 
@@ -271,8 +268,6 @@ void testEquivalentYears() {
   Expect.equals(0, dt.microsecond);
   Expect.equals("2036-07-18 13:20:00.000", dt.toString());
 
-  if (!supportsMicroseconds) return;
-
   dt = new DateTime.utc(2035, 1, 1, 0, 0, 0, 0, 1);
   Expect.equals(SECONDS_YEAR_2035 * 1000000 + 1, dt.microsecondsSinceEpoch);
   dt = new DateTime.utc(2034, 12, 31, 23, 59, 59, 999, 999);
@@ -334,8 +329,6 @@ void testUTCGetters() {
   Expect.equals(1, dt.millisecond);
   Expect.equals(0, dt.microsecond);
 
-  if (!supportsMicroseconds) return;
-
   dt = new DateTime.fromMicrosecondsSinceEpoch(-9999999999, isUtc: true);
   Expect.equals(1969, dt.year);
   Expect.equals(12, dt.month);
@@ -493,8 +486,6 @@ void testSubAdd() {
   Expect.equals(true, dt1 == dt3);
   Expect.equals(false, dt1 == dt2);
 
-  if (!supportsMicroseconds) return;
-
   dt1 = new DateTime.fromMillisecondsSinceEpoch(1305140315000, isUtc: true);
   dt2 = dt1
       .add(new Duration(microseconds: 3 * Duration.microsecondsPerSecond + 5));
@@ -513,8 +504,7 @@ void testSubAdd() {
 }
 
 void testUnderflowAndOverflow() {
-  int microsecond = supportsMicroseconds ? 499 : 0;
-  final dtBase = new DateTime(2012, 6, 20, 12, 30, 30, 500, microsecond);
+  final dtBase = new DateTime(2012, 6, 20, 12, 30, 30, 500, 499);
 
   // Millisecond
   print("  >>> Millisecond+");
@@ -719,8 +709,6 @@ void testUnderflowAndOverflow() {
   Expect.equals(dtBase1.millisecond, dtTick.millisecond);
   Expect.equals(dtBase1.microsecond, dtTick.microsecond);
 
-  if (!supportsMicroseconds) return;
-
   // Microsecond
   print("  >>> Microsecond+");
   dt = new DateTime(dtBase.year, dtBase.month, dtBase.day, dtBase.hour,
@@ -943,48 +931,24 @@ void testDateStrings() {
   Expect.equals(0, dt1.microsecond);
   Expect.equals(true, dt1.isUtc);
   dt1 = DateTime.parse("1999-01-02 23:59:59.99951");
-  if (supportsMicroseconds) {
-    Expect.equals(1999, dt1.year);
-    Expect.equals(1, dt1.month);
-    Expect.equals(2, dt1.day);
-    Expect.equals(23, dt1.hour);
-    Expect.equals(59, dt1.minute);
-    Expect.equals(59, dt1.second);
-    Expect.equals(999, dt1.millisecond);
-    Expect.equals(510, dt1.microsecond);
-  } else {
-    // We only support millisecond. If the user supplies more data (the "51"
-    // here), we round.
-    Expect.equals(1999, dt1.year);
-    Expect.equals(1, dt1.month);
-    Expect.equals(3, dt1.day);
-    Expect.equals(0, dt1.hour);
-    Expect.equals(0, dt1.minute);
-    Expect.equals(0, dt1.second);
-    Expect.equals(0, dt1.millisecond);
-    Expect.equals(0, dt1.microsecond);
-  }
+  Expect.equals(1999, dt1.year);
+  Expect.equals(1, dt1.month);
+  Expect.equals(2, dt1.day);
+  Expect.equals(23, dt1.hour);
+  Expect.equals(59, dt1.minute);
+  Expect.equals(59, dt1.second);
+  Expect.equals(999, dt1.millisecond);
+  Expect.equals(510, dt1.microsecond);
   Expect.equals(false, dt1.isUtc);
   dt1 = DateTime.parse("1999-01-02 23:58:59.99951Z");
-  if (supportsMicroseconds) {
-    Expect.equals(1999, dt1.year);
-    Expect.equals(1, dt1.month);
-    Expect.equals(2, dt1.day);
-    Expect.equals(23, dt1.hour);
-    Expect.equals(58, dt1.minute);
-    Expect.equals(59, dt1.second);
-    Expect.equals(999, dt1.millisecond);
-    Expect.equals(510, dt1.microsecond);
-  } else {
-    Expect.equals(1999, dt1.year);
-    Expect.equals(1, dt1.month);
-    Expect.equals(2, dt1.day);
-    Expect.equals(23, dt1.hour);
-    Expect.equals(59, dt1.minute);
-    Expect.equals(0, dt1.second);
-    Expect.equals(0, dt1.millisecond);
-    Expect.equals(0, dt1.microsecond);
-  }
+  Expect.equals(1999, dt1.year);
+  Expect.equals(1, dt1.month);
+  Expect.equals(2, dt1.day);
+  Expect.equals(23, dt1.hour);
+  Expect.equals(58, dt1.minute);
+  Expect.equals(59, dt1.second);
+  Expect.equals(999, dt1.millisecond);
+  Expect.equals(510, dt1.microsecond);
   Expect.equals(true, dt1.isUtc);
   dt1 = DateTime.parse("0009-09-09 09:09:09.009Z");
   Expect.equals(9, dt1.year);
@@ -1079,22 +1043,15 @@ void testDateStrings() {
       () => DateTime.parse("275760-09-14T00:00:00.000Z"));
   Expect.throwsFormatException(
       () => DateTime.parse("275760-09-13T00:00:00.001Z"));
-  if (supportsMicroseconds) {
-    Expect.throwsFormatException(
-        () => DateTime.parse("275760-09-13T00:00:00.000001Z"));
-  } else {
-    dt1 = DateTime.parse("275760-09-13T00:00:00.000001Z");
-  }
-
+  Expect.throwsFormatException(
+      () => DateTime.parse("275760-09-13T00:00:00.000001Z"));
   // first valid time; should not throw.
   dt1 = DateTime.parse("-271821-04-20T00:00:00.000Z");
   Expect.throwsFormatException(
       () => DateTime.parse("-271821-04-19T23:59:59.999Z"));
 
-  if (supportsMicroseconds) {
-    Expect.throwsFormatException(
-        () => DateTime.parse("-271821-04-19T23:59:59.999999Z"));
-  }
+  Expect.throwsFormatException(
+      () => DateTime.parse("-271821-04-19T23:59:59.999999Z"));
 }
 
 void testWeekday() {
@@ -1159,14 +1116,11 @@ void testToStrings() {
   test("1970-01-01", "00:00:00.000");
   test("1969-12-31", "23:59:59.999");
   test("1969-09-09", "00:09:09.009");
-
-  if (supportsMicroseconds) {
-    test("2000-01-01", "12:00:00.000001");
-    test("-2000-01-01", "12:00:00.000001");
-    test("1970-01-01", "00:00:00.000001");
-    test("1969-12-31", "23:59:59.999999");
-    test("1969-09-09", "00:09:09.009999");
-  }
+  test("2000-01-01", "12:00:00.000001");
+  test("-2000-01-01", "12:00:00.000001");
+  test("1970-01-01", "00:00:00.000001");
+  test("1969-12-31", "23:59:59.999999");
+  test("1969-09-09", "00:09:09.009999");
 }
 
 void testIsoString() {
@@ -1188,8 +1142,6 @@ void testIsoString() {
   d = new DateTime.utc(-10000, 1, 1, 23, 59, 59, 999);
   Expect.equals("-010000-01-01T23:59:59.999Z", d.toIso8601String());
 
-  if (!supportsMicroseconds) return;
-
   d = new DateTime(9999, 1, 1, 23, 59, 59, 999, 999);
   Expect.equals("9999-01-01T23:59:59.999999", d.toIso8601String());
   d = new DateTime(-9999, 1, 1, 23, 59, 59, 999, 999);