In many EU countries a contract does not actually end if you continue to show up to do work in mutual (implicit) agreement with the managers at the company you work for. It would constitute an implicit extension of the contract, effectively renewing it under the same terms for the same duration (with a maximum of 1 year IIRC).
I can vouch for this. As a freelancer I actually had exactly this happen: I was working for a client with a time-limited contract. The contract expired on New Year's Eve and they failed to renew it so I expected to have been terminated.
One week later they send me an e-mail asking when I'll be back from vacation. They refused to renew the contract (which explicitly said it required a formal written agreement to be renewed) but wanted me to keep working for them. So I went back to them and they kept paying me.
Several months later we had a disagreement and they claimed the terms of the original contract no longer applied because they hadn't renewed them. But my lawyer confirmed that in fact the contract was still valid because they implicitly extended it and the requirement for a formal renewal was invalidated (they failed to provide a new contract so the extension was still subject to the terms of the initial contract even though it had expired).
We didn't go all the way in court so I can't say whether this would have held up, but they ended up reaching an agreement with me where they pretty much gave up on everything except my legal fees, so I guess their lawyer wasn't too hopeful.
