calends

calends is a library for durations, intervals and other calendar related operations. It is designed to work with chrono.

Durations of time

A [RelativeDuration] is a unit of time that has some ability to be applied to a date to produce another date.

```rust use calends::RelativeDuration; use chrono::NaiveDate;

// This will allow you to add one month and then go back two days from the added month let rd = RelativeDuration::months(1).with_days(-2);

// It also compatible with NaiveDate asserteq!( NaiveDate::fromymd(2022, 1, 1) + rd, NaiveDate::from_ymd(2022, 1, 30) ); ```

Recurrence & Rules

[Recurrence] allows you to specify a ruleset for how events (dates) repeat in time.

```rust use calends::{Recurrence, Rule}; use chrono::NaiveDate;

let date = NaiveDate::fromymd(2022, 1, 1); let end = NaiveDate::fromymd(2022, 3, 1);

let mut recur = Recurrence::withstart(Rule::monthly(), date).until(end); asserteq!(recur.next(), Some(NaiveDate::fromymd(2022, 1, 1))); asserteq!(recur.next(), Some(NaiveDate::fromymd(2022, 2, 1))); asserteq!(recur.next(), None); ```

Intervals

An interval is a span of time that can be bound or unbound. This means that you can iterate until the beginning/end of the time. However in practice this will be limited by chronos types.

This will likely be used to do things like iterate by week, month, quarter, or year.

```rust use calends::{Interval, IntervalLike, RelativeDuration}; use calends::interval::marker::{End, Start}; use chrono::NaiveDate;

let start = NaiveDate::from_ymd(2022, 1, 1); let duration = RelativeDuration::months(1);

let mut interval = Interval::from_start(start, duration);

asserteq!(interval.start(), start); asserteq!(interval.end(), NaiveDate::from_ymd(2022, 1, 31));

// Intervals are also iterable because they always have a duration! // they are inclusive so they return the current time span first

let next = interval.next().unwrap();

asserteq!(next.start(), NaiveDate::fromymd(2022, 1, 1)); asserteq!(next.end(), NaiveDate::fromymd(2022, 1, 31));

let next = interval.next().unwrap();

asserteq!(next.start(), NaiveDate::fromymd(2022, 2, 1)); asserteq!(next.end(), NaiveDate::fromymd(2022, 2, 28));

```

In combination with RelativeDuration you can do things such as iterate the second to last day of the month.

```rust use calends::{Interval, RelativeDuration}; use chrono::NaiveDate;

let duration = RelativeDuration::months(1).withdays(-2); let start = NaiveDate::fromymd(2022, 1, 1);

let mut interval = Interval::from_start(start, duration); ```

License: MIT