Kronos is a tool for calculating date/times. It is meant to give a concrete date for questions like "When is the 2nd Monday of June?", or "What was the 3rd to last day-of-the-week of past February?".
To answer these questions kronos composes TimeSequence iterators. These are infinite sequences into the past and the future which you can pin to a particular instant and get resulting time Ranges.
Lets first define a TimeSequence that represents any and all Mondays. Then use it to get an iterator of all future Mondays from a specific t0 instant onward.
```rust
// Reference time: Tuesday, 5th Feb 2019
let t0 = chrono::NaiveDate::fromymd(2019, 2, 5)
.andhms(0, 0, 0);
// A sequence for Mondays let mondays = kronos::Weekday(1);
// First Monday after t0 reference time mondays.future(&t0).next() ```
The previous example would return a Range which represents an open-ended time interval [start, end). Ranges also have a Grain that specifies the resolution of the start and end instants.
Examples of a Range could be Aug 26th 2018. - It has a resolution of Grain::Day, - starts on 2018/08/26 00:00:00, - ends on 2018/08/27 00:00:00
TimeSequencesSome simple TimeSequences can be built almost out of thin air. For example:
- Weekday(2) a sequence for Tuesdays.
- Month(6) a sequence for all June months.
- Grains(Grain::Day) a sequence to iterate over days.
More comples TimeSequences can be created by combining other sequences. For example:
- NthOf(2, Weekday(1), Month(6)) creates a sequence for "the second Mondays of June".
- LastOf(1, Weekend, Grains(Grain::Year)) for "last weekend of the year".
- Intersect(Weekday(1), NthOf(28, Grains(Grain::Day), Grains(Grains::Month))) for "all Monday 28th".
Other compositions allow unions, intersections, intervals, exceptions, etc. Please check each module's tests for examples on how to use them.