The plain statement that Ulrich Zwingli was born at Wildhaus, Switzerland on 1 January 1484, conceals as much as it states. Royalty apart, it is relatively seldom that a birthday can be so surely stated as this, for in the fifteenth and later centuries evidence of date of birth was hard to come by; in some cases a good deal of guesswork is involved. In Zwingli's case however, that New Year's Day, 1 January, was his birthday, and that this was in 1484 can be demonstrated from adequate documentary evidence.

Almost the most unusual thing about the early years of life in the middle ages was survival; most mothers had many children, relatively few of whom grew up. Many were born and died, leaving almost no trace of their existence. The perils of babyhood over, the chief risk was plague and epidemic, less virulently dangerous, obviously, in small villages, but constantly anticipated. When they survived, most children grew up at home with their parents, very much in the open air, and were treated with natural affection combined with a good deal of conventional neglect. Farmyard life was normal, even for city dwellers, and these were relatively few. Parentage, of course, mattered enormously, place of birth rather less, at a time when defined frontiers were almost unknown and even political allegiance was often uncertain. Nowhere in the small civilised world of western Europe was this more apparent than in Switzerland.