Calendar

Ambitiously also adding the proper fallback in 7.6 compat mode would be another improvement in style. I don't think a behaviour as clearly inconcistent with itself is anything to stick around with though, even if it doesn't break the letter of the standard it vaguely references.

It is a lot easier to get "2007-08-14T09:26:22", if you wanted that, from replace(Calendar.ISO_UTC.Second(time())->format_time()," ","T") than the output of Calendar.ISO_UTC.Second(time())->format_iso_short() so I don't quite buy in to your argument, and the given output looks are too suspicious to be anything I would depend on prior to having verified in docs that it is indeed intended that way.

Possible, but not worth keeping around API cruft for, IMO.