I dont trust your link in the slightest  Its not even from a source at the UK Government or from a reliable commercial source like a Zimbabwean vendor  The longest day can vary based on your latitude occasionally longitude and your altitude relative to cloud cover levels over certain mountain peaks and the presence of reptiles and other large fauna  Things are not as simple as you make them out to be my friend hope you dont mind me calling you that but the fact remains facts are fact and the change regarding May rd was identified as one by someone at the Wikipedia machine  With editors such as you at the helm I trust that implicitly  I also trust the authorized and authenticated go code I had to make such a posting  The facts are indisputable  Best wishes