Calculate with fix width like 180 is not a good idea, because this value is not equal in all skin resolutions and fonts.

So the developer has use the "00:00 - 00:000" as a solution and it is not an issue.
You don't have to frantically look for another…

Maybe this was my mistake, as I tested these changes on an image that already had some differences from the original image.

However, I found a solution for the original Images that maintains the correct "HH:MM - HH:MM" format while ensuring the text is…

Have you tested your changes to "00:00 - 00:00" ?
I think not

If i change the textTpl to "00:00 - 00:00" the width for the time-text is to small.
(screenshots from Default-FHD skin)

Thank you for your comment! I agree with you that the purpose of textTpl is to calculate the required width for the addtimedisplay text correctly, and the idea of using a string to determine the maximum width makes sense.
However, I think "00:00 - 00:000"…

I think it is not an issue.
The textTpl is used to calculate the needed addtimedisplayWidth to show the addtimedisplay-Text.
With "00:00 - 00:000" you can set the max. of width for all values (begin - end time) to get the best calculated needed width.
…