Step 1: Recall the year directly:
1919 A.D. marks: Jallianwala Bagh Massacre / Rowlatt Act.
Step 2: Provide brief context:
In 1919, the repressive Rowlatt Act was passed, and on 13 April 1919 General Dyer's troops fired on an unarmed gathering at Jallianwala Bagh, Amritsar, killing hundreds -- a turning point that galvanised the Indian freedom movement.
Final Answer:
\[ \boxed{\text{Jallianwala Bagh Massacre / Rowlatt Act}} \]