See http://en.wikipedia.beta.wmflabs.org/wiki/Special:Version
Specifically, MediaWiki's version says "1.26alpha (c32e5fd) 13:32, 12 August 2015" and Flow's says "1.1 (e62cb0b) 01:03, 12 August 2015". The current UTC time is 22:38, 13 August 2015, so MW core is about 33 hours behind and Flow about 46 hours.