In both the PC/Mobile game and on Consoles (PS4/XB1), Events occur weekly on Mondays, coinciding with the weekly PvP rank reset.
Originally, Events lasted for a fortnight, but became weekly from 18 May 2015 onwards.
On 14 December 2016, game Update 2.2 introduced a weekly Weapon Bundle that makes available an older Event weapon previously tied to the featured Kingdom. A Weapon Bundle pack is featured every week in the Shop, under the Weekly Event tab. Cost is $5 USD each for the Event weapon along with a few miscellaneous consumables.
Currently the $5 Bundle typically contains the Weapon itself, plus 1000 Gold, 400 Souls, 10 Gold Keys, 2 Event Keys, and 25 VIP points.