how to convert time for different timezones

so i am making a messaging app but i cannot get the code done right

this is the send Button:

sendbutton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View _view) {
                if (img == 0) {
                    if (edittext1.getText().toString().equals("")) {
                        
                    }
                    else {
                        Numberrr++;
                        mm = new HashMap<>();
                        mm.put("username", get_name);
                        mm.put("pfp", get_pfp);
                        mm.put("messages", edittext1.getText().toString().trim());
                        mm.put("user_uid", FirebaseAuth.getInstance().getCurrentUser().getUid());
                        mm.put("number", String.valueOf((long)(Numberrr)));
                        cal = Calendar.getInstance();
                        mm.put("time", new SimpleDateFormat("E hh:mm s").format(cal.getTime()));
                        ch.push().updateChildren(mm);
                        mm.clear();
                        edittext1.setText("");
                        lastText.edit().putString("Lasttext", String.valueOf((long)(Numberrr))).commit();
                    }
                }
                else {
                    store.child(imgName).putFile(Uri.fromFile(new File(imgPath))).addOnFailureListener(_store_failure_listener).addOnProgressListener(_store_upload_progress_listener).continueWithTask(new Continuation<UploadTask.TaskSnapshot, Task<Uri>>() {
                        @Override
                        public Task<Uri> then(Task<UploadTask.TaskSnapshot> task) throws Exception {
                            return store.child(imgName).getDownloadUrl();
                        }
                    }).addOnCompleteListener(_store_upload_success_listener);
                    progressbar1.setVisibility(View.VISIBLE);
                    sendbutton.setEnabled(false);
                    edittext1.setEnabled(false);
                }
            }
        });

and this is part of the code for the ListView:

            LayoutInflater _inflater = (LayoutInflater) getBaseContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View _view = _v;
            if (_view == null) {
                _view = _inflater.inflate(R.layout.messgebubble, null);
            }

            final LinearLayout time = _view.findViewById(R.id.time);
            final TextView textview1 = _view.findViewById(R.id.textview1);
            final LinearLayout linear4 = _view.findViewById(R.id.linear4);
            final TextView timetext = _view.findViewById(R.id.timetext);
            final LinearLayout left = _view.findViewById(R.id.left);
            final LinearLayout linear1 = _view.findViewById(R.id.linear1);
            final de.hdodenhof.circleimageview.CircleImageView circleimageview1 = _view.findViewById(R.id.circleimageview1);
            final TextView message = _view.findViewById(R.id.message);
            final ImageView imageview1 = _view.findViewById(R.id.imageview1);
            final TextView SystemText = _view.findViewById(R.id.systemtext);
            final LinearLayout system = _view.findViewById(R.id.system);
//This is to set the time on text view 
            timetext.setText(new Sim("MM/yyyy hh:mm:ss").format(_data.get((int)_position).get("time").toString()));
//end

so im trying to get messages to display the right time for messages while in different timezone

e.g. if someone is in (UTC+1) but the message is from (UTC+5)and the message was sent at 17:35(UTC+5) it would show 17:35 but it should be showing 14:35… as you can tell this will cause a lot of problems in code also.

edit: a revision

Answer

Your question is not clear. But likely these points will help you:

• Never use the legacy date-time classes such as Date, Calendar, SimpleDateFormat, etc. They are terrible. Use only the modern java.time classes defined in JSR 310.
• To track a moment, a specific point on the timeline, do so “in UTC” (an offset of zero hours-minutes-seconds from UTC), using the java.time.Instant class.
• To serialize a moment textually for data storage or data exchange, use the standard ISO 8601 format. Usually best to do so in UTC, using Instant#toString and Instant.parse.

Here is some brief code. But search to learn more. All this has been covered many many times already on Stack Overflow.

Capture current moment

Use java.time.Instant to represent a moment as seen in UTC.

Instant instant = Instant.now() ;  // Capture the current moment as seen in UTC. 
String s = instant.toString() ;    // Generate text in standard ISO 8601 format. 

Parse

Here we parse text in standard ISO 8601 format.

Instant instant = Instant.parse( "2022-04-19T15:30:14.348767Z" ) ;

Adjust into time zone

For presentation to the user, you may want to adjust to a particular time zone. Same moment, same point on the timeline, different wall-clock time.

ZoneId z = ZoneId.of( "America/Edmonton" ) ;
ZonedDateTime zdt = instant.atZone( z ) ;

Generate text

Standard format

To generate text in standard format, simply call toString.

instant.toString(): 2022-04-19T15:30:14.348767Z

zdt.toString(): 2022-04-19T09:30:14.348767-06:00[America/Edmonton]

Actually that last one is an wise extension of the standard format, appending the name of the time zone in square brackets.

Localized format

To generate text in a localized format, use DateTimeFormatter.ofLocalizedDateTime.

FormatStyle style = FormatStyle.SHORT ;
Locale locale = Locale.CANADA_FRENCH ;  // Or Locale.US or new Locale( "fr" , "MA" ) (French in Morocco), etc.
DateTimeFormatter f = DateTimeFormatter.ofLocalizedDateTime( style ).withLocale( locale ) ;
String output = zdt.format( f );

See this code run live at IdeOne.com.

output: 22-04-19 09 h 30

You can of course specify a custom format via DateTimeFormatter.ofPattern. (Search to learn more.) But automatically localizing might make your life simpler.