https://en.wikipedia.org/wiki/Special:Block/192.0.2.16?safemode=1&useskin=vector or https://test.wikipedia.org/wiki/Special:Block/Amory?safemode=1&useskin=vector
Selecting a dropdown for the expiration gives a console warning:
Deprecation warning: value provided is not in a recognized RFC2822 or ISO format. moment construction falls back to js Date(), which is not reliable across all browsers and versions. Non RFC2822/ISO date formats are discouraged and will be removed in an upcoming major release. Please refer to http://momentjs.com/guides/#/warnings/js-date/ for more info. Arguments: [0] _isAMomentObject: true, _isUTC: false, _useUTC: false, _l: undefined, _i: 6 months, _f: undefined, _strict: undefined, _locale: [object Object] deprecate/<@https://en.wikipedia.org/w/load.php?lang=en&modules=ext.centralNotice.geoIP%7Cext.centralauth.ForeignApi%7Cext.centralauth.centralautologin.clearcookie%7Cext.cx.eventlogging.campaigns%7Cext.echo.api%2Cinit%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.uls.common%2Ccompactlinks%2Cinterface%2Cpreferences%2Cwebfonts%7Cjquery%2Cmoment%2Coojs%2Coojs-ui-core%2Coojs-ui-widgets%7Cjquery.client%2Ccookie%2ClengthLimit%2CtextSelection%7Cjquery.uls.data%7Cmediawiki.ForeignApi%2CString%2CTitle%2CUri%2Capi%2Cbase%2Ccldr%2Ccookie%2Cexperiments%2Chtmlform%2CjqueryMsg%2Clanguage%2Cstorage%2Cuser%2Cutil%2Cwidgets%7Cmediawiki.ForeignApi.core%7Cmediawiki.editfont.styles%7Cmediawiki.htmlform.ooui%7Cmediawiki.libs.pluralruleparser%7Cmediawiki.page.ready%7Cmediawiki.special.block%7Cmediawiki.ui.button%7Cmediawiki.widgets.DateInputWidget%2CNamespacesMultiselectWidget%2CSelectWithInputWidget%2CTitlesMultiselectWidget%2CUserInputWidget%2Cdatetime%2Cexpiry%7Cmediawiki.widgets.DateInputWidget.styles%7Coojs-ui-widgets.icons%7Coojs-ui.styles.icons-content%2Cicons-editing-advanced%2Cicons-editing-core%2Cicons-moderation%2Cicons-movement%7Cskins.vector.js%7Cuser.defaults&skin=vector&version=ac44y:262:770...[snipped]
Also happens when I enter start to enter a value in "other time" or when reblocking, since that auto-selects the prior block expiry.
This is a warning from the moment library, but I'm not sure why it's in suddenly in play here.