//! A cron expression parser and schedule explorer
//! # Example
//! ```
//! use cron::Schedule;
//! use chrono::Utc;
//! use std::str::FromStr;
//!
//! fn main() {
//! // sec min hour day of month month day of week year
//! let expression = "0 30 9,12,15 1,15 May-Aug Mon,Wed,Fri 2018/2";
//! let schedule = Schedule::from_str(expression).unwrap();
//! println!("Upcoming fire times:");
//! for datetime in schedule.upcoming(Utc).take(10) {
//! println!("-> {}", datetime);
//! }
//! }
//!
//! /*
//! Upcoming fire times:
//! -> 2018-06-01 09:30:00 UTC
//! -> 2018-06-01 12:30:00 UTC
//! -> 2018-06-01 15:30:00 UTC
//! -> 2018-06-15 09:30:00 UTC
//! -> 2018-06-15 12:30:00 UTC
//! -> 2018-06-15 15:30:00 UTC
//! -> 2018-08-01 09:30:00 UTC
//! -> 2018-08-01 12:30:00 UTC
//! -> 2018-08-01 15:30:00 UTC
//! -> 2018-08-15 09:30:00 UTC
//! */
//! ```
/// Error types used by this crate.
pub use crate;
pub use crate TimeUnitSpec;