SyncReference currentServerTimeRef=WilddogSync.getInstance().getReference("servertimestamp");
//存入当前云端时间戳
currentServerTimeRef.setValue(ServerValue.TIMESTAMP)

SyncReference connectedRef = WilddogSync.getInstance().getReference(".info/serverTimeOffset");
      connectedRef.addValueEventListener(new ValueEventListener() {
          @Override
          public void onDataChange(DataSnapshot dataSnapshot) {
              long offset = (long) dataSnapshot.getValue(Long.class);
              long estimatedServerTimeMs=System.currentTimeMillis()+offset;
          }

          @Override
          public void onCancelled(SyncError syncError) {

          }
      });