Problem

new Date(undefined) and new Date('not a date') produce an invalid Date object whose .getTime() returns NaN. Previously prepareValue() would pass such a date straight through to dateToString() / dateToStringUTC(), which format each NaN time component with padStart(), producing the meaningless string:

0NaN-NaN-NaNTNaN:NaN:NaN.NaN+NaN:NaN

Postgres cannot parse that and responds with a cryptic server-side error. The bug is especially hard to track down because the garbled string originates silently in JavaScript — the user has no indication that an invalid Date was passed in the first place.

Fixes #3318.

Fix

Add an isNaN(val.getTime()) guard in the isDate branch of prepareValue() and throw an informative error immediately:

if (isDate(val)) {
  if (isNaN(val.getTime())) {
    throw new Error('date is invalid')
  }
  // ... existing serialization
}

The error surfaces at the JavaScript call site, making the root cause immediately obvious.

Tests

Added two unit tests in packages/pg/test/unit/utils-tests.js:

• new Date(undefined) → throws /date is invalid/
• new Date('not a date') → throws /date is invalid/