Thank you for your comment, Pieter. A while ago I was subscribing to the idea that a ship was considered to be "under construction" until the day (hour and minute, like in the delivery documents) it was delivered to her owners, just like you wrote, but then I checked the category description for "Ships under construction", that said "Do not upload to this category photos of completed new ships undergoing sea trials or awaiting delivery. These belong in the relevant ship category, and must comply with the Site Standards for that category."
The way I understand it now, a "fit for purpose" ship goes into the appropriate category, with her sea trials being the separation between the categories.

Cheers

Vlad

Technically the ship is still under construction, i.e. owned by the shipyard. The actual delivery/hand over date would be the separation between the categories ship under construction and tankers built form 2021-2030. There are variants you can think of f.i. completed but not handed over, but laid up after completion, (ships under construction) or handed over but laid up after delivery (tanker built 2021-2030),. One can also think of laid up upon delivery in 2020 (for argument sake) but started trading in 2021. These are all examples not unusual during the Seventies collapse of the tanker market, but rarely seen nowadays, but I think it is a thing to keep in mind when shooting newbuild(ing) ships.