Soon the Nexus will be full of heroes battling it out for glory and to help celebrate, we’re sharing free XP! Use the XP to unlock your favorite Master Skin, or secure level 30 to play Hero League. Players who log in to the Americas region between the hours of 12:01 AM PDT on June 2nd and 11:59 PM PDT on June 9th will receive a 25% XP boost.
http://us.battle.net/heroes/en/blog/19508171/xp-boost-event-5-29-2015
