新增新旧日期时间 API 之间，以及 joda-time 与新日期时间 API 之间转换的方法。

src/test/java/xyz/zhouxy/plusone/commons/util/DateTimeUtilTests.java

@@ -0,0 +1,58 @@
+package xyz.zhouxy.plusone.commons.util;
+
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import org.joda.time.DateTime;
+import org.joda.time.DateTimeZone;
+import org.joda.time.format.DateTimeFormat;
+import org.joda.time.format.DateTimeFormatter;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class DateTimeUtilTests {
+
+    private static final Logger log = LoggerFactory.getLogger(DateTimeUtilTests.class);
+
+    @Test
+    void testLocalNowStr() {
+        log.info(DateTimeUtil.nowStr("yyyy/MM/dd HH:mm:ss.SSS"));
+    }
+
+    @Test
+    void testToJoda() {
+        LocalDateTime now = LocalDateTime.now();
+        log.info("now: {}", now);
+        org.joda.time.LocalDateTime now2 = DateTimeUtil.toJodaLocalDateTime(now);
+        log.info("now2: {}", now2);
+    }
+
+    @Test
+    void testToInstant() {
+        Instant now = DateTimeUtil.toInstant(System.currentTimeMillis());
+        String str = DateTimeUtil.toString("yy-M-d HH:mm:ss.SSS", now);
+        log.info(str);
+    }
+
+    @Test
+    void testToJodaDateTime() {
+        DateTime jodaDateTime = DateTimeUtil.toJodaDateTime(Instant.now(), ZoneId.of("null"));
+        log.info("jodaDateTime: {}", jodaDateTime);
+    }
+
+    @Test
+    void test() {
+        Instant now = Instant.now();
+        DateTime jodaDateTime = DateTimeUtil.toJodaDateTime(now, ZoneId.of("America/New_York"));
+        DateTimeFormatter formatter = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss.SSS");
+        log.info(formatter.print(jodaDateTime));
+        log.info(jodaDateTime.getZone().toString());
+        log.info(jodaDateTime.toString());
+        log.info("==========================================");
+        org.joda.time.Instant instant = new org.joda.time.Instant(System.currentTimeMillis() - 500000);
+        log.info(instant.toString());
+        log.info(DateTimeUtil.toJavaInstant(instant).toString());
+        log.info(DateTimeUtil.toZonedDateTime(instant, DateTimeZone.forID("America/New_York")).toString());
+    }
+}