What timezone are timestamps on blog posts in?

https://matrix.org/blog/2023/06/membership-program/ for example says "13:00", but I know for a fact that's not local time. We should either append timezone information, or use a local time calculation instead. Alternatively, do we even need timestamps? Aren't datestamps fine?

Start with the example blog post at https://matrix.org/blog/2023/06/membership-program/ and trace how its timestamp is rendered in the website source. Determine whether timestamps include timezone information or should be replaced by datestamps; done means the chosen convention is applied consistently and the example is no longer ambiguous.

Written by the indexing model from the issue text.