# C768 — Compare row rounding with date-grid rounding

## Question

Can rounding already calculated dates reproduce the source chronology?

## Inputs

```json
{
  "grid_anchor": 1406
}
```

## Sources

```json
[
  "File51a §16.2; C754–757"
]
```

## Opened utc

2026-09-28T01:58:17.376412+00:00

## Results

```json
{
  "diagnostic": {
    "path": "model/date_grid_diagnostic.json",
    "sha256": "ac040f2ee4e2718dc6af24e48a39d46edbff3525e3a215e0f5ab2e1a1b8bd876",
    "bytes": 2216
  },
  "mismatch_counts": {
    "MT_native_OFF": 11,
    "LXX_native_ON": 7,
    "SP_native_OFF": 17
  },
  "MT_examples": {
    "Noah": {
      "grid": 6381,
      "row": 6386
    },
    "Abraham": {
      "grid": 2436,
      "row": 2431
    }
  }
}
```

## Finding

A nearest1/6 date-grid projection fails at11 of26 MT boundaries. Rounded chronology depends on the source path, not just the final Actual date.

## Reassessment

Test subdivision dependence over an informative complete source subpath.

## Checks

```json
{
  "counts": true,
  "Noah": true
}
```

## Closed utc

2026-09-28T01:58:17.376999+00:00

## Record provenance

Exact record hash: `cac6e7b1574e63f5dd512752e6bc3c640cbee44356a8c157d9de97aa79ed803a`

Source journal: `Research_Cycles/C0732_C0831/journal.json`