I believe the answer is Classicism, a period that, according to most estimations, lasted approximately from 1730 to 1820. Concertos and sonatas existed in the Baroque period as well, but symphony's major development falls into this era, with Joseph Haydn, the so-called Father of Symphony. Sonatas and concertos were standardized by getting the structure of 3 or 4 movements, which usually went from fast to slow to fast. Symphonies usually consisted of 4 movements, with fast-slow-minuetto-fast structure. This basic standard persisted through Romanticism as well, although it was upgraded.