Weird date thing on Tuesdays

When the day is Tuesday, the open evenings page (https://www.57north.org.uk/open-evenings) doesn't show the current Tuesday, but shows the following Tuesday twice.

<img width="1189" height="970" alt="Image" src="https://github.com/user-attachments/assets/4ea3a37f-66a4-4b3a-bf46-a812d3c94267" />