The current implementation of SpecialMobileDiff.php uses the revisionasof template with only one parameter. The German revisionasof template expects the date and time passed in $2 and $3 respectively, see implementation of getRevisionHeader() in DifferenceEngine.php for details.

This causes the following text to be displayed for the version link
Version vom $2, $3 Uhr
instead of the expected
Version vom 3. Mai 2019, 11:40 Uhr

(see e.g. https://de.m.wikipedia.org/wiki/Spezial:Mobiler_Unterschied/188172886)

Developer notes

includes/diff/DifferenceEngine.php should be used as a guideline:

$timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
$dateofrev = $lang->userDate( $revtimestamp, $user );
$timeofrev = $lang->userTime( $revtimestamp, $user );

$header = $this->msg(
        $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
        $timestamp,
        $dateofrev,
        $timeofrev
)->escaped();

In MobileFrontend:

$td = $this->getLanguage()->userTimeAndDate( $ts, $user );

$templateData = [
        "revisionLinkLabel" => $this->msg( 'revisionasof', $td )->escaped(),

QA steps

Check the english ui:

1. Visit https://readers-web-staging.wmflabs.org/w/index.php?title=Hellooooo&oldid=692&mobileaction=toggle_view_mobile&uselang=en
2. Make sure there are no weird characters like dollar signs $ present in the revision date. e.g. It should be like Revision as of 15:25, 29 April 2019

Check the german ui:

1. https://readers-web-staging.wmflabs.org/w/index.php?title=Hellooooo&oldid=692&mobileaction=toggle_view_mobile&uselang=de
2. Again check that there are no weird characters present in the revision date that shouldn't be there. You should NOT see Version vom $2, $3 Uhr

QA Results