How to adjust clock on VW T4 dashboard

Ever since the hour went back in October, the clock below the rev counter in our 2001 VW T4 Topaz has been wrong.

Turning the adjuster next to it (as per the VW manual) has no effect. As we've only had the van since June, I'm not sure whether I have ever needed to adjust it before.

I'm guessing I'm missing something *really* obvious

Do you need to push or pull the knob as well as turning it?

hi
on my t4 you have use the point of a pencil or pen and push the button in the required number if time to adjust the time, hope this helps
mike
vwt4

After much pushing, pulling, twisting (in combination with ignition off / ignition on / engine running), I've found the answer:
I found that it's not enough to just twist the knob until it clicks - you have to twist it *really hard* - then the digits on the clock reluctantly change