Write docs

Cargo.lock

@@ -925,8 +925,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9ea835d29036a4087793836fa931b08837ad5e957da9e23886b29586fb9b6650"
 
 [[package]]
-name = "dust"
+name = "dust-lang"
-version = "0.3.0"
+version = "0.1.0"
 dependencies = [
  "chrono",
  "clap",

src/value/mod.rs

@@ -1,3 +1,4 @@
+//! Types that represent runtime values.
 use crate::{
     error::{Error, Result},
     Function, Table, Time, ValueType, VariableMap,

src/value/time.rs

@@ -1,3 +1,12 @@
+//! Representation of a moment in time.
+//!
+//! Whale represent time values correctly. To do this, there must be a clear separation between
+//! monotonic timestamps, naive times that do not know their locale and those that have a timezone.
+//!
+//! Only monotonic time instances are guaranteed not to repeat, although and Instance can be used to
+//! create and of these variants. Users generally want the timezone included, so the `as_local` is
+//! included, which will use no timezone offset if one is not available.
+
 use std::{
     fmt::{self, Display, Formatter},
     time::{Instant, SystemTime},