Refers to the period of being a child; a straightforward compound of 子供 (child) and 時代 (era/period).
Memories of my childhood are always happy.
He spent his childhood in the countryside.
子供時代 is the everyday, casual way to refer to one's childhood, while 幼少 is a formal, written term emphasizing the very early years.
子供時代 is a general, colloquial word for one's whole childhood, whereas 幼少期 is more formal and focuses on the earliest part of it.
Compound of 子供 (child) and 時代 (era, period).