April 13: 102 years since the Jallianwala Bagh Massacre; 61 years since Transit 1-B's launch, the first satellite navigation system; 51 years since the "crippling" of Apollo 13, leading to the principal accident and complications; 4 years since the GBU-43/B Massive Ordnance Air Blast's, the largest ever non-nuclear weapon, is dropped!
April 14: 63 years since Sputnik 2, carrying Laika, de-orbited from Earth's orbit; 40 years since STS-1, the first Space Shuttle mission, returned!
April 15: 98 years since Insulin, whose deficiency causes Diabetes Mellitus, became generally available for diabetic people's use; 69 years since the first flight of the B-52 Stratofortress, probably the USAF's longest-serving long-range bomber; 66 years since the founding of McDonald's!