# RefDateTime.isBefore

Check if the current state of a RefDateTime is before another DateTime.

## Signatures

```ts
export declare const isBefore: {
    (that: DateTime.DateTime): <E, R>(ref: RefDateTime<E, R>) => RefSubject.Computed<boolean, E, R>;
    <E, R>(ref: RefDateTime<E, R>, that: DateTime.DateTime): RefSubject.Computed<boolean, E, R>;
};
```

## Why

Check if the current state of a RefDateTime is before another DateTime. The operation remains
attached to the RefSubject's versioned state boundary.

## Ownership and lifetime

The is before view retains no independent state. An Effect read samples the source once; Fx
observation follows later pushes and its observing Scope owns subscription cleanup.