optimise gregorian

[conradludgate]

The loops that were originally there didn't optimise well. This new code optimises much better with less branches

The one regression is a false positive and on re-runs switched between + and -

[codecov-commenter]

Codecov Report

Base: 78.75% // Head: 78.88% // Increases project coverage by +0.12% 🎉

Coverage data is based on head (4c7a0f4) compared to base (896243f).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #160      +/-   ##
==========================================
+ Coverage   78.75%   78.88%   +0.12%     
==========================================
  Files           9        9              
  Lines        2349     2363      +14     
==========================================
+ Hits         1850     1864      +14     
  Misses        499      499              

Impacted Files	Coverage Δ
src/epoch.rs	88.07% <100.00%> (+0.14%)	⬆️

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[ChristopherRabotin]

Wow, this is a fantastic improvement in speed! Thanks!

I'll merge this is right away. Do you need this to be on crates.io right now or can it wait a bit?

[conradludgate]

I'm in no rush, I saw this on reddit and thought I'd help out. I'm on a mission to make all time libraries efficient :)

[ChristopherRabotin]

If there are any features you need that would make you consider using hifitime instead of another library at TrueLayer, let me know. My use case is quite narrowly focused on engineering and scientific applications, so I may miss the broader requirements that folks need, but I would really like it if hifitime became as useful to the Rust community as time.rs or chrono.

[conradludgate]

I will definitely let you know. The kind of features we make use of are RFC3339 formatting, and recently working with dates only - eg adding months or finding the monday of week 12. I understand this use case is quite different to what hifitime is currently intending