There isn't a site bug. Before paying you had to check the date. You can call the customerservice or reach them by Facebook, X, and chat.

Have you watched the video in the link? There its clearly visible that TS selects the 1st of January and after continuing the webshop says the tickets are valid on the 31st of December. Then TS tries again selecting the 2nd of January and the webshop says on the following page that the tickets are valid for the 1st of January.

Not very smart however that TS continued purchasing the tickets after that, but there clearly is some bug in the website.

@Daniel de video was niet zo duidelijk. Wel dat de tickets gekocht werden voor 31/12 /23, maar mij is niet duidelijk door het schokkige beeld of die opname voor of na betaling was. Wanneer je een reis selecteert in de planner voor 4 uur ‘s ochtends met de datum 1 januari 2024 dan krijg je het ticket op de datum van de dag dat je deze selecteert. Om 1 januari 2024 op het ticket te krijgen moet je een reis selecteren op 1 januari vanaf 4 uur.

Zelfde als je een reis op 1 januari 2024 om 3 uur wilt maken, dan moet je in de planner naar 31 december 2023 kijken.

Dit is geen bug, maar dit is hoe het bij NS werkt.

Not sure how you deduct that the TS was trying to buy a ticket before 4am. From watching the video the TS was trying to buy the ticket from this page https://www.ns.nl/en/routes/eindhoven-to-amsterdam and not from the travel planner. The linked page does not allow to select specific journey times, simply the date - and then the video indeed shows the date automatically reverting back one day after clicking on ‘ see ticket price’. That being said, I cannot replicate the error/bug today on my laptop today.

Best to check with customer service as mentioned by MoDe if they are willing to refund.

Dat is wel degelijk een bug. Op je ticket hoort de datum te staan die je gekozen hebt.

Maybe it has something to do with the time zone as Bucharest is one hour ahead of the Netherlands?

Was thinking the same - perhaps the computer time of the TS (when buying) was already at Jan 1st, while Dutch time (and hence the NS webshop) was still at Dec 31st?

Maybe, but NS should be able to handle such a case. If not, then that's also a bug.

This was clearly a hiccup/bug.

For @Costin Nicolae, there was likely no need to buy e-tickets because you can also use the credit card you ordered the tickets with in public transport for the same price, billed the day afterwards for all journeys on that day.

t only needs to support contactless (NFC) payments. A phone wallet (Apple Pay or Google Pay) will work, too. See https://ovpay.nl/en I assume your fellow traveller has a debit/credit card, too.

NS Customer Service (phone, chat, social media) contact info here.

Translated: 

Acesta a fost în mod clar un sughiț/buc.

Pentru @Costin Nicolae, probabil că nu a fost nevoie să cumpere bilete electronice pentru că poți folosi și cardul de credit cu care ai comandat biletele în transportul public la același preț, facturat a doua zi pentru toate călătoriile din ziua respectivă.

trebuie doar să accepte plăți fără contact (NFC). Un portofel de telefon (Apple Pay sau Google Pay) va funcționa, de asemenea. Vedeți https://ovpay.nl/en Presupun că colegul dvs. de călătorie are și un card de debit/credit.