fix http

hutool-core/src/main/java/cn/hutool/core/date/DateTime.java

@@ -268,6 +268,10 @@ public class DateTime extends Date {
 	 * @return 如果此对象为可变对象，返回自身，否则返回新对象
 	 */
 	public DateTime offset(DateField datePart, int offset) {
+		if(DateField.ERA == datePart){
+			throw new IllegalArgumentException("ERA is not support offset!");
+		}
+
 		final Calendar cal = toCalendar();
 		//noinspection MagicConstant
 		cal.add(datePart.getValue(), offset);

hutool-core/src/test/java/cn/hutool/core/date/DateUtilTest.java

@@ -645,6 +645,7 @@ public class DateUtilTest {
 		DateTime startDate = DateUtil.parse("2019-12-01 17:02:30");
 		DateTime endDate = DateUtil.parse("2019-12-02 17:02:30");
 		int length = 3;
+		//noinspection deprecation
 		boolean expired = DateUtil.isExpired(startDate, DateField.DAY_OF_YEAR, length, endDate);
 		Assert.assertTrue(expired);
 	}