How about this?

A) Much like Ninja Exam, but with Lightning, Water and Earth attribute battles, with each attribute having 50 levels. The first phase will start on April 18th and training will unlock in 3 rounds (Lightning training will open April 18th, Water Training April 20th and Earth training on the 22nd). The mode will open for one week.

They are stating the first phase will start on April 18th, this is from Nature Training description. (Sorry for the English)