[SOLVED] Changing time and date format on sddm login/lock screen

This apply to my configuration

KDE Frameworks 5.55.0
Qt 5.9.7 (built against 5.9.7)
kf5-config: 1.0
The xcb windowing system

plasmashell 5.12.8

Leap 15.1
kernel 4.12.14-lp151.28.48-default

Documentations :

After reading this :

which cites also :
    Wrong time format in plasma5 lock screen

Searching in internet I found this about Qt date time format

Current ‘look and feel’ theme : opensuse
Configuration files in : /usr/share/plasma/look-and-feel/org.openSUSE.desktop

As ROOT after having done a backup just in case, edit the current running theme file : /usr/share/plasma/look-and-feel/org.openSUSE.desktop/contents/components/Clock.qml

To change the time from the standard format to hh:mm:ss 24h clock
find a line like :

text: Qt.formatTime(timeSource.data"Local"]"DateTime"])
change to :
text: Qt.formatTime(timeSource.data"Local"]"DateTime"], "hh:mm:ss")

To change the date from the default locale long date format to yyyy/mm/dd
find a line like :

text: Qt.formatDate(timeSource.data"Local"]"DateTime"], Qt.DefaultLocaleLongDate);
change to :
text: Qt.formatDate(timeSource.data"Local"]"DateTime"], "yyyy/MM/dd");

Hit Ctrl+Alt+L to lock your screen and see the change immediately.

This should be applied on each other theme in the folder /usr/share/plasma/look-and-feel if wanted.

I hope it helps someone.

Detail on date time format can be found here :

The format specification is described at [Qt.formatDateTime](https://doc.qt.io/qt-5/qml-qtqml-qt.html#formatDateTime-method).

Note I have forgotten :
Upgrades will overwrite the changes to the Breeze SDDM theme. A better way is copy the Breeze theme under another name.
And this is true for any theme for any distrib.