How long does nameserver propagation take?

Nameserver propagation is different from the propagation of a simple DNS record change (see How long does it take for DNS changes to propagate?): when you change a domain's nameservers entirely (for example switching from another provider's nameservers to park1.eureg.ro / park2.eureg.ro), the information has to be updated both at the registry (EURid/RoTLD/other) and in the cache of DNS servers around the world.

The change is usually visible at the registry level almost instantly, but full global propagation can take anywhere from a few hours up to 24-48 hours, depending on the TTL (Time To Live) previously set on the old nameservers and how aggressively various internet providers cache DNS answers.

During this period it's possible for the site or email to behave inconsistently (some visitors see the new version, others the old one) — this is normal behavior, not an error.