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# holoscan::TagTime

> Represent the deterministic logical order of local activation candidates.

Represent the deterministic logical order of local activation candidates.

Unlike [Tag](tag), `TagTime` is an ordering coordinate. Valid baseline records order lexicographically by logical_ns and then microstep. The zero record is a valid coordinate; absence, when required by a containing contract, must use a separate validity mechanism. Reserved bits never participate in ordering and must be zero for a baseline-supported record. Ordering remains a strict weak relation for every bit pattern so generic ordered algorithms remain well-defined even when a malformed or future-version record is inspected before validation.

`TagTime` is a fixed-size, standard-layout, trivially copyable record. It is local ordering evidence, not physical or capture time. It owns no resources, performs no allocation, and is safe to copy, hash, or compare concurrently.

```cpp showLineNumbers={false}
#include <holoscan/tag.hpp>
```

---

## Methods

### valid \[#valid]

```cpp showLineNumbers={false}
bool holoscan::TagTime::valid() const noexcept
```

Return whether this record uses the supported baseline representation.

**Returns:** `true` when reserved is zero; otherwise `false`.

---

## Member variables

| Name         | Type            | Description                                           |
| ------------ | --------------- | ----------------------------------------------------- |
| `logical_ns` | `std::int64_t`  | Signed logical nanosecond coordinate.                 |
| `microstep`  | `std::uint32_t` | Deterministic order among candidates at `logical_ns`. |
| `reserved`   | `std::uint32_t` | Record-version reservation; must be zero in baseline. |