Switch to using java.time classes & make work for dates past 2038.

src/main/java/com/jcraft/jsch/SftpATTRS.java

@@ -26,7 +26,11 @@
 
 package com.jcraft.jsch;
 
-import java.util.Date;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.Locale;
 
 /*
  * uint32 flags uint64 size present only if flag SSH_FILEXFER_ATTR_SIZE uint32 uid present only if
@@ -122,13 +126,20 @@ else if ((permissions & S_IXGRP) != 0)
   }
 
   public String getAtimeString() {
-    Date date = new Date(((long) atime) * 1000L);
-    return (date.toString());
+    return toDateString(Integer.toUnsignedLong(atime));
   }
 
   public String getMtimeString() {
-    Date date = new Date(((long) mtime) * 1000L);
-    return (date.toString());
+    return toDateString(Integer.toUnsignedLong(mtime));
+  }
+
+  private static DateTimeFormatter DTF =
+      DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss zzz yyyy", Locale.ROOT);
+
+  static String toDateString(long epochSeconds) {
+    Instant instant = Instant.ofEpochSecond(epochSeconds);
+    ZonedDateTime zdt = ZonedDateTime.ofInstant(instant, ZoneId.systemDefault());
+    return DTF.format(zdt);
   }
 
   public static final int SSH_FILEXFER_ATTR_SIZE = 0x00000001;

src/test/java/com/jcraft/jsch/SftpATTRSTest.java

@@ -0,0 +1,38 @@
+package com.jcraft.jsch;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Date;
+import java.util.Random;
+import org.junit.jupiter.api.Test;
+
+public class SftpATTRSTest {
+
+  private final Random random = new Random();
+
+  @Test
+  public void testToDateString0() {
+    String expected = new Date(0L).toString();
+    String actual = SftpATTRS.toDateString(0L);
+    assertEquals(expected, actual);
+  }
+
+  @Test
+  public void testToDateStringNow() {
+    long now = System.currentTimeMillis() / 1000L;
+    String expected = new Date(now * 1000L).toString();
+    String actual = SftpATTRS.toDateString(now);
+    assertEquals(expected, actual);
+  }
+
+  @Test
+  public void testToDateStringRandom() {
+    for (int i = 0; i < 1000000; i++) {
+      int j = random.ints(Integer.MIN_VALUE, Integer.MAX_VALUE).findFirst().getAsInt();
+      long l = Integer.toUnsignedLong(j);
+      String expected = new Date(l * 1000L).toString();
+      String actual = SftpATTRS.toDateString(l);
+      assertEquals(expected, actual);
+    }
+  }
+}