Ubuntu19.04 can't set Date & Time and User , has been locked

What exactly is the text of the message box requesting the password?

If you have been granted admin rights (by membership of the "sudo" or "admin" groups), then you can gain admin rights if you confirm a message like the one that you got with your own password. The message box clearly states the username for which it needs the password (in the center).

If you are not member of the "admin" or "sudo" groups, then you cannot change system settings.

See also https://help.ubuntu.com/community/RootSudo

The password you need here is the password you set at install time. The one you log in with when the system boots.

I have the rights of sudo, and also I'm in root groups.

The message box is like this:
-----------------------------------------------------------------------------------------------------------
Authentication Required

  Authentication is required ti change user data
  Administrator
  Password: (here it let me to input a password)

Cancel(button) Authenticate(button)

-------------------------------------------------------------------------------------------------------
this is a new system , and i don't have a administrator user.
so now, I can't change the system date & time or User Setting.

it is useless to input the user login password .

What output do you receive for the following commands (to be executed in a terminal window):

id
sudo id

# wanghuaiyu @ wanghyu-Ubuntu in ~ [17:04:24]
$ id
uid=1000(wanghuaiyu) gid=1000(wanghuaiyu) groups=1000(wanghuaiyu),0(root)

# wanghuaiyu @ wanghyu-Ubuntu in ~ [17:04:25]
$ sudo id
uid=0(root) gid=0(root) groups=0(root)

Sorry for taking so long to reply, because of The Chinese National Day.

I tried it on another computer （Ubuntu 18.04LTS) , In Setting Dialog -> Details ->Data & Time and User, it is locked too. But the login password can unlock it.

but it's useless in Ubuntu19 , I'm not sure what went wrong.

What is the output of the commands

id
sudo id

on the Ubuntu 18.04 system, where this is working?

on the Ubuntu 18.04 , id and sudo id shows like this:

# wanghuaiyu @ ubuntu in ~ [17:27:11]
$ id
uid=1000(wanghuaiyu) gid=0(root) groups=0(root)

# wanghuaiyu @ ubuntu in ~ [17:27:25]
$ sudo id
[sudo] password for wanghuaiyu:
uid=0(root) gid=0(root) groups=0(root)

It seems the group id is different

In my opinion the settings on both systems are wrong.

As far as I know they should look similar to
$ id
uid=1000(wanghuaiyu) gid=1000(wanghuaiyu) groups=1000(wanghuaiyu),27(sudo)[+eventually more groups like lp, lpadmin, ...]