title: History of mobile phones
context: Prior to 1973, mobile telephony was limited to phones installed in cars and other vehicles.[19] Motorola was the first company to produce a handheld mobile phone.  On April 3, 1973, Martin Cooper, a Motorola researcher and executive, made the first mobile telephone call from handheld subscriber equipment, placing a call to Dr. Joel S. Engel of Bell Labs, his rival.[25][26][27]  The prototype handheld phone used by Dr. Cooper weighed 1.1 kilograms (2.4lb) and measured 23 by 13 by 4.5 centimetres (9.1 by 5.1 by 1.8in). The prototype offered a talk time of just 30 minutes and took 10 hours to re-charge.[28]
question: When was the first cellphone developed?
answers: April 3, 1973