Before epoch

beforeEpoch validates that a Date instance represents a moment before the Unix epoch (January 1, 1970, 00:00:00 UTC).

It performs a strict type check ensuring the value is a Date instance, then validates that the timestamp is less than 0 (Unix epoch). If the value is not a Date or represents the epoch or later, the rule emits a single validation event. Otherwise, it produces no validation output.

Signature

Through the API:

.beforeEpoch()

And internally:

export const beforeEpoch: ValidationRule
(value: unknown, path: FieldPath) => Promise<ReadonlyArray<JaneEvent>>

Events

Event code	Description
date.not.date	Value is not a Date instance
date.is.before-epoch	Date represents Unix epoch or later

Design rationale

• Provides a strict, predictable pre-Unix epoch validation.
• First ensures the value is a Date instance.
• Then validates the timestamp is strictly less than 0.
• Useful for historical data or legacy system compatibility.
• Never coerces or normalizes — validation is explicit and opt-in.
• Emits exactly one event per failure for clarity and composability.
• Async-compatible and returns a readonly array of JaneEvent objects.

Invoke

beforeEpoch runs only when explicitly included in a boundary or pipeline. It does not run automatically.

The rule activates when:

• The value is any JavaScript value.
• If the value is not a Date instance, emits date.not.date.
• If the value is a Date but represents epoch or later, emits date.is.before-epoch.
• If the value is a Date before the Unix epoch → returns an empty result set.

Examples

Pre-epoch date

await beforeEpoch(new Date("1969-12-31"), "$");
// → []

Post-epoch date

await beforeEpoch(new Date("1970-01-01"), "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "date.is.before-epoch",
//       path: "$",
//       ...
//     }
//   ]

Non-Date value

await beforeEpoch("1969-12-31", "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "date.not.date",
//       path: "$",
//       ...
//     }
//   ]