Nothing about the popularity of this submission on this day is ironic[1]. As far as the temporal component goes the article was published today on a popular website. "News" submissions often receive the most attention close to the day of publication.
I do not think there is any cultural explanation for "irony" in this case. You seem to imply that the obvious upvoting demographic for this article are sabbath-observing jewish readers of HN. Are gentiles not expected to be interested in other cultures? How interesting do you think an article about the sabbath is to someone that observes the sabbath once a week? Most importantly, the article is about much more than observing the sabbath. I think it is possible that you read the headline and just blurted out the first shower thought that came to mind. Did you read the article in its entirety?
[1] Irony: fig. A condition of affairs or events of a character opposite to what was, or might naturally be, expected; a contradictory outcome of events as if in mockery of the promise and fitness of things.
