Add Quarter period

[matthieugomez]

This is the same as #35519, except that it is rebased (the only difference is to resolve the NEWS file conflict). Sorry to open a different pull request but I cannot modify the original pull request anymore — not sure what I did wrong.

[PallHaraldsson]

I was looking at the code, and noticed:

julia/stdlib/Dates/src/query.jl

Line 655 in e36b7b4

const QUARTERDAYS = (0, 90, 181, 273)

I think this is still wrong, for a leap year:

julia> dayofquarter(Date(2020, 4, 1))
2

[matthieugomez]

Good point! I think you could open an issue about it --- this is not something I have introduced with my changes.

[matthieugomez]

Thanks!

[PaulSoderlind]

Did you forget adding the following to adjusters.jl, or was it intentional?:

Base.trunc(dt::Date, p::Type{Quarter}) = firstdayofquarter(dt)
Base.trunc(dt::DateTime, p::Type{Quarter}) = DateTime(trunc(Date(dt), Quarter))

[matthieugomez]

Indeed, I forgot to add these methods. Could you open a pull request to add them?

[PaulSoderlind]

done. #38277