I found this, it looks like it’s not really possible because the structure of the two services are pretty different:

https://lemmy.world/post/12903915

The article: https://www.politico.eu/article/norway-arctic-region-asks-eu-commission-for-26-hour-day/

How would the new time zones work in practice? Wenche Pedersen, the mayor of Vadsø who authored the letter, is unsure.

“We haven’t thought a lot about that” she said. “The clock will go from 12 to 13… and we have to see how this will go. I don’t think they’re going to say yes so we haven’t thought about all the details.”

Huh. Great idea.

Not sure about your request of being open source, but you can try this one which doesn’t have tracking or ads:

https://one-clock.com/