私の把握してるかぎり、当時ガントチャートはなかったはず……
plantuml.com
それもそのはず、以下のように、出来立てホヤホヤの新機能です。
12 Apr, 2018: New Gantt diagram features.
@startgantt project starts the 2018/04/09 saturday are closed sunday are closed 2018/05/01 is closed 2018/04/17 to 2018/04/19 is closed [Prototype design] lasts 14 days [Test prototype] lasts 4 days [Test prototype] starts at [Prototype design]'s end [Prototype design] is colored in Fuchsia/FireBrick [Test prototype] is colored in GreenYellow/Green @endgantt