# add

Add a Duration to the current state of a RefDateTime.

## Signatures

```ts
export declare const add: {
    (parts: Partial<{
        readonly millis?: number;
        readonly seconds?: number;
        readonly minutes?: number;
        readonly hours?: number;
        readonly days?: number;
        readonly weeks?: number;
        readonly months?: number;
        readonly years?: number;
    }>): <E, R>(ref: RefDateTime<E, R>) => RefSubject.Computed<DateTime.DateTime, E, R>;
    <E, R>(ref: RefDateTime<E, R>, parts: Partial<{
        readonly millis?: number;
        readonly seconds?: number;
        readonly minutes?: number;
        readonly hours?: number;
        readonly days?: number;
        readonly weeks?: number;
        readonly months?: number;
        readonly years?: number;
    }>): RefSubject.Computed<DateTime.DateTime, E, R>;
};
```

## Why

Add a Duration to the current state of a RefDateTime. The operation remains attached to the
RefSubject's versioned state boundary.

## Ownership and lifetime

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