week_numbers in all calendars

[LXde]

hello supporters,

is there a possibility to show the weeknumbers in all calendars (across dotproject, inclusive the little popup-cal).
this is a very important feature for me.
can anyone tell me how to do this (where and how i have to edit the code).

i found something in /calendar/week_view.php, but i dont know how to
implement this in all calendarviews.
... any suggestions ?...

best regards
LXde