Granularity of time in current column adjustable?

[jogi-k]

We are using kanboard for organizing our Repair Cafe.
We usually agree with the guests to spend around half to three quarters of an hour on a defect object and try to repair it.
Therefore the duration of tasks in columns with the current default granularity of 15 mins / 30 mins is sometimes to rough.
Is there the possibility to adjust the granularity of the Standard Task view which shows duration directly on the card, but as stated, to rough for our purpose.
If not by config, can someone point me into the right direction in Source Code.
It's about 10-15 years ago, that I last was working with PHP, but with the proper direction I could imagine to survive :-) and try myself...

Thanks
Jogi

[jogi-k]

Answering myself...
Not yet been able to run myself locally from source-code, but I found
app/Helper/DateHelper.php
with a function called
public function age($timestamp, $now = null),
which seems to do what I am looking for, so I hope I can patch this according to my needs.