Crate time

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Feature flags

This crate exposes a number of features. These can be enabled or disabled as shown in Cargo’s documentation. Features are disabled by default unless otherwise noted.

Reliance on a given feature is always indicated alongside the item definition.

std (enabled by default, implicitly enables alloc)

This enables a number of features that depend on the standard library.
alloc (enabled by default via std)

Enables a number of features that require the ability to dynamically allocate memory.
macros

Enables macros that provide compile-time verification of values and intuitive syntax.
formatting (implicitly enables std)

Enables formatting of most structs.
parsing

Enables parsing of most structs.
local-offset (implicitly enables std)

This feature enables a number of methods that allow obtaining the system’s UTC offset.
large-dates

By default, only years within the ±9999 range (inclusive) are supported. If you need support for years outside this range, consider enabling this feature; the supported range will be increased to ±999,999.

Note that enabling this feature has some costs, as it means forgoing some optimizations. Ambiguities may be introduced when parsing that would not otherwise exist.

If you are using this feature, please leave a comment on this discussion with your use case. If there is not sufficient demand for this feature, it will be dropped in a future release.
serde

Enables serde support for all types except Instant.
serde-human-readable (implicitly enables serde, formatting, and parsing)

Allows serde representations to use a human-readable format. This is determined by the serializer, not the user. If this feature is not enabled or if the serializer requests a non-human-readable format, a format optimized for binary representation will be used.

Libraries should never enable this feature, as the decision of what format to use should be up to the user.
serde-well-known (implicitly enables serde/alloc, formatting, and parsing)

Enables support for serializing and deserializing well-known formats using serde’s #[with] attribute.
rand

Enables rand support for all types.
quickcheck (implicitly enables alloc)

Enables quickcheck support for all types except Instant.

One pseudo-feature flag that is only available to end users is the unsound_local_offset cfg. As the name indicates, using the feature is unsound, and may cause unexpected segmentation faults. Unlike other flags, this is deliberately only available to end users; this is to ensure that a user doesn’t have unsound behavior without knowing it. To enable this behavior, you must use RUSTFLAGS="--cfg unsound_local_offset" cargo build or similar. Note: This flag is not tested anywhere, including in the regular test of the powerset of all feature flags. Use at your own risk. Without this flag, any method that requires the local offset will return the Err variant.