Why does .weekday date component start at 1 in swift?

Question

The .weekday component starts at 1 (sunday = 1, monday = 2 etc...) and I'm interested if anyone knows why. It seems that usually in programming things start at 0.

Answer 1

The reason for zero based indexing in programming dates back to the time when programs were written in machine language or assembly code. It is a reflexion of the base+displacement capability of memory access from CPU registers. It was maintained in low level programming languages (such as C) that were essentially a bridge to assembly code. Zero based indexing also provides much simpler index manipulation when processing a one dimensional array (or memory block) as a multidimensional matrix. That being said, it is still just a convention. Some languages (such as Pascal) use one based indexing and normal human beings don't start numbering things at zero.

I don't know the fundamental reason for the numbering of weekdays being based on 1 but I strongly suspect that it is more consistant (and practical) to use with calendars where day numbers within a month, and months with a year are also 1 based. It would be very confusing to manipulate days and months as zero based indexes. Given this, weekdays should follow the same conventions.