chore: Use local date time instead of time

Author: lqiu96

google-cloud-logging/src/main/java/com/google/cloud/logging/testing/RemoteLoggingHelper.java

@@ -101,7 +101,7 @@ public static RemoteLoggingHelper create() {
    * <p>Format: {Instant}_{name}_{UUID}
    */
   public static String formatForTest(String name) {
-    String now = DateTimeFormatter.ISO_INSTANT.format(Instant.now());
+    String now = DateTimeFormatter.ISO_LOCAL_DATE.format(Instant.now());
     return now + "_" + name + "_" + UUID.randomUUID().toString().substring(0, 8);
   }
 

google-cloud-logging/src/test/java/com/google/cloud/logging/BaseSystemTest.java

@@ -50,14 +50,14 @@ static void beforeClass() {
 
   @AfterAll
   static void afterClass() throws Exception {
-    // Use a cutoff of ~6 hours based on the log name. Any logs that were created before the cutoff
+    // Use a cutoff of a day based on the log name. Any logs that were created before the cutoff
     // is from a previous invocation of the test and was unable to be properly deleted.
     Page<String> logPage = logging.listLogs();
     for (String logName : logPage.iterateAll()) {
-      Instant cutoff = Instant.now().minus(6, ChronoUnit.HOURS);
+      Instant cutoff = Instant.now().minus(1, ChronoUnit.DAYS);
       String logCreateTimeString = logName.split("_")[0];
       Instant logCreateTimeInstant =
-          (Instant) DateTimeFormatter.ISO_INSTANT.parse(logCreateTimeString);
+          (Instant) DateTimeFormatter.ISO_LOCAL_DATE.parse(logCreateTimeString);
       if (logCreateTimeInstant.isBefore(cutoff)) {
         logging.deleteLog(logName);
       }