Plus an minus methods on `LocalTime` and `LocalDateTime` types

[nesk]

The Instant type supports addition and subtraction of a Duration:

fun example(now: Instant) {
    now - 5.seconds
    now + 5.seconds
}

The LocalDate type supports addition and subtraction of DatePeriod:

fun example(now: LocalDate) {
    now - DatePeriod(days = 2)
    now + DatePeriod(days = 2)
}

However, the LocalTime doesn't support any addition or subtraction, which requires cumbersome code to do these changes:

fun example(now: LocalTime) {
    LocalTime.fromSecondOfDay(now.toSecondOfDay() - 5)
    LocalTime.fromSecondOfDay(now.toSecondOfDay() + 5)
}

What about adding a TimePeriod type? This would allow to write code like this:

fun example(now: LocalTime) {
    now - TimePeriod(seconds = 5)
    now + TimePeriod(seconds = 5)
}

This would also pave the way for addition and subtraction of the LocalDateTime type:

fun example(now: LocalDateTime) {
    now - DateTimePeriod(days = 2, seconds = 5)
    now + DateTimePeriod(days = 2, seconds = 5)
}

[dkhalanskyjb]

Please read https://github.com/Kotlin/kotlinx-datetime?tab=readme-ov-file#date--time-arithmetic

If you have some specific code that needs LocalTime arithmetics, please share it here or on the Kotlin Slack, and we'll help you reach an idiomatic and robust solution.

[nesk]

Sorry, I did not see this section in the documentation 😓

Seems fine to me, I will use Instant for arithmetics!