From https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Flow-compare-revisions-revision-header/en : as per https://www.mediawiki.org/wiki/Localisation#Separate_times_from_dates_in_sentences , translators need to know the grammatical nature of a message a parameter. Saying things like
$1 - date and timestamp, formatted as most are in Flow. That is, a human-readable timestamp is shown.
is completely useless.
We need a template like https://translatewiki.net/wiki/Template:Doc-months which will list all the cases and embed all the involved messages via {{msg-mw}}. As far as I know the messages are:
"just-now": "just now",
"hours-ago": "$1 {{PLURAL:$1|hour|hours}} ago",
"minutes-ago": "$1 {{PLURAL:$1|minute|minutes}} ago",
"seconds-ago": "$1 {{PLURAL:$1|second|seconds}} ago",
"monday-at": "Monday at $1",
"tuesday-at": "Tuesday at $1",
"wednesday-at": "Wednesday at $1",
"thursday-at": "Thursday at $1",
"friday-at": "Friday at $1",
"saturday-at": "Saturday at $1",
"sunday-at": "Sunday at $1",
"today-at": "$1",
"yesterday-at": "Yesterday at $1",
Apparently, getHumanTimestamp() assumes that all of these can be translated with an adverbial syntagma in any language.
The followup task will be to add this template to the qqq of all messages using a getHumanTimestamp() parameter, by editing the corresponding /qqq pages on translatewiki.net.