[thunfisch]

It's using a slash because that's how ISO 8601 defines time intervals. https://en.wikipedia.org/wiki/ISO_8601#Time_intervals

[funnybeam]

Thanks for linking that. I’m a big proponent of using ISO 8601 but had either missed or completely forgotten about it specifying a format for intervals.

Note that ISO also permits a double hyphen as the interval separator which is hugely preferable to me personally and also works with file names (as mentioned in that Wikipedia article)

[account42]

Doesn't look like IOS 8601 allows spaces though so this is still an ad-hoc syntax.

RFC3339 at least lets you replace the ugly T with a space but also doesn't specify any spaces around "/" for ranges.