Add Time value type in System

[Gimly]

Rationale

Today, we have a DateTime struct in System that represents a specific date and time, which supports time zones. We also have a TimeSpan object that represents a duration (for example the time between two DateTime). I feel that we are missing a simple Time object that represents a time of day, without it being linked to a particular day.

There are a lot of reasons for representing time without dates. Alarms of an alarm clock, work shifts in a company, etc. T-Sql has a time type that cannot today be mapped to a type in .Net.

DateTime.TimeOfDay today returns a TimeSpan, but it feels out of place, TimeSpan represents a duration and not a specific time of day.

Implementation

Implementation would be pretty simple, it would have properties Hours, Minutes, Seconds, Milliseconds, Ticks and a few comparison / transformation methods.

DateTime.TimeOfDay would return this new Time struct instead of the current TimeSpan.

[khellang]

This is already implemented in corefxlab. Also, see https://github.com/dotnet/corefx/issues/2116 and dotnet/corefxlab#1740. It'll probably make its way into corefx Very Soon™ 😄

[jnm2]

DateTime.TimeOfDay would return this new Time struct instead of the current TimeSpan.

I totally wish this was possible, but that would make people's existing code crash at runtime or break on recompile:

TimeSpan timeOfDay = CalculateDateTime().TimeOfDay;
// Use timeOfDay

[khellang]

The current proposed implementation of System.Time has an explicit cast from TimeSpan, which calls this out.

[Gimly]

Great! Didn't find #14744 when I did a search, clear that I wasn't the first to think about that issue 😄.

So... should I close this issue?

[AlexRadch]

I do not see any advantages on TimeSpan. It seems like to add FourBits type. Also some days can have additional seconds https://en.wikipedia.org/wiki/Leap_second .
Can TimeOfDay return more then 24 hours or not?

[khellang]

I don't think so. None of the BCL date and time types supports leap seconds, AFAIK.

[jnm2]

Noda Time doesn't support leap seconds either.

[Clockwork-Muse]

Also, for the most part, at the level we're dealing with, we're only concentrating on "human" time, where, while leap seconds are part of (some standards of) official civil time, most people don't know or care about them.

That's if the host system even gives you a way to detect them in the first place. On Windows, it essentially says, "hey, the value I got from NTP says I'm a second off now, for some unknown reason, let me do what I normally do when I'm a second off, and gradually align my clock". I'd imagine some Linux distributions do something similar.

[GSPP]

A Date data type would be handy as well.

[Clockwork-Muse]

@GSPP - Date is there too.

[ilmax]

Can anyone from MS shed a bit of light about what's happening with System.Date and System.Time? They are in corefxlab since a long tim, but I wasn't able to find any news about promoting them to the BCL.

Are they gonna make it? It would be nice to have a type that represent a date as a first class citizen in the BCL

[ilmax]

@terrajobst I may have missed something but I don't know what's the story about these two types and I'm not sure why they didn't made their way into the framework yet, can you please share some info?