Extra slow Utc to Local conversion about chrono

[pitdicker]

Breakdown with Intel VTune (lowered to 500_000 records because I was impatient):

We may want to cache the Windows timezone data instead of calling GetTimeZoneInformationForYear on every conversion.

[djc]

Can I assume that you're on Windows?

[i-sinister]

That would be currect. Currently working on POC on windows. Haven't tried on linux yet.

[i-sinister]

Checked in WSL:

> cat /etc/os-release
Ubuntu 22.04.4 LTS
...
> rustc --version
rustc 1.75.0 (82e1608df 2023-12-21) (built from a source tarball)
> cargo --version
cargo 1.75.0
> cargo run --release
convert to utc: 3.764427601s
convert to local: 25.472681589s

Much better but still slower then c# version.

[pitdicker]

With EnumDynamicTimeZoneInformation we can get the timezone data.

Edit: With GetDynamicTimeZoneInformationEffectiveYears we can get the range of years to get timezone data for.

[djc]

We may want to cache the Windows timezone data instead of calling GetTimeZoneInformationForYear on every conversion.

I guess we should generalize the cache mechanism we use on the Unix side?