Switch to time crate, add file sizes (#329)

* Switch to time crate, add file sizes

* Update deps, adjust pack format

* Run formatter, fix clippy

src/util/time_ser.rs

@@ -0,0 +1,42 @@
+//! Use the well-known [RFC3339 format] when serializing and deserializing an [`OffsetDateTime`].
+//!
+//! Use this module in combination with serde's [`#[with]`][with] attribute.
+//!
+//! [RFC3339 format]: https://tools.ietf.org/html/rfc3339#section-5.6
+//! [with]: https://serde.rs/field-attrs.html#with
+
+use core::fmt;
+use core::marker::PhantomData;
+
+use serde::{de, Deserializer, Serialize, Serializer};
+use time::Format::Rfc3339;
+use time::OffsetDateTime;
+
+/// Serialize an [`OffsetDateTime`] using the well-known RFC3339 format.
+pub fn serialize<S: Serializer>(
+    datetime: &OffsetDateTime,
+    serializer: S,
+) -> Result<S::Ok, S::Error> {
+    datetime.format(Rfc3339).serialize(serializer)
+}
+
+/// Deserialize an [`OffsetDateTime`] from its RFC3339 representation.
+pub fn deserialize<'a, D: Deserializer<'a>>(
+    deserializer: D,
+) -> Result<OffsetDateTime, D::Error> {
+    deserializer.deserialize_any(Visitor(PhantomData))
+}
+
+pub(super) struct Visitor<T: ?Sized>(pub(super) PhantomData<T>);
+
+impl<'a> de::Visitor<'a> for Visitor<OffsetDateTime> {
+    type Value = OffsetDateTime;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        formatter.write_str("an `OffsetDateTime`")
+    }
+
+    fn visit_str<E: de::Error>(self, value: &str) -> Result<OffsetDateTime, E> {
+        OffsetDateTime::parse(value, Rfc3339).map_err(E::custom)
+    }
+}