No. That isn't possible. We no longer load two copies of the same node.
My guess is this node started life as a copy of an existing nodes code base and they both declare this variable as a global - which is bad practice regardless.
The question is which node is it clashing with.
Once approach to narrow it down would be to open http://localhost:1880/nodes in a new browser tab. You'll get a largely blank page. Then view source of the page and search for
calcDuration. If you find it, scroll up to find the section break telling you which node that bit of code is from... Hopefully you'll see what I mean.