Date: Date Only Timezone Annotation Tool

Description

Attach a nonempty single-line timezone annotation to a validated date.

A fixed UTC offset differs from a named timezone whose rules can vary by date. A zone-like label or signed-zero offset also carries metadata that a numeric minute total alone cannot express.

Attach a nonempty single-line timezone annotation to a validated date.

When to use this tool

Use Date: Date Only Timezone Annotation when inspecting a supplied offset or timezone annotation.

How to use the tool and how it works

Enter date, timezoneAnnotation. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read result. Expand result to inspect the returned fields.

Attach a nonempty single-line timezone annotation to a validated date. Preserve the supplied annotation up to 128 characters and return resolvesInstant = false.^[1]

Input field	Meaning and units	Accepted input
date	Date	Required. Text. Real Gregorian YYYY-MM-DD; years 0001-9999 accepted. Implementation limit: 8192 Unicode code points and 16384 UTF-16 code units.
timezoneAnnotation	Timezone Annotation	Required. Text. Implementation limit: 8192 Unicode code points and 16384 UTF-16 code units.

Output field	Interpretation	Returned shape
result	Returned object; expand its named members below.	Required. Object.
result.date	Date	Calculated result member: string.
result.timezoneAnnotation	Timezone Annotation	Calculated result member: string.
result.resolvesInstant	Always false: a date and unchecked annotation do not identify an instant.	Calculated result member: boolean.

json

{
  "input": {
    "date": "2024-01-01",
    "timezoneAnnotation": "Europe/London"
  },
  "output": {
    "result": {
      "date": "2024-01-01",
      "timezoneAnnotation": "Europe/London",
      "resolvesInstant": false
    }
  }
}

Limitations and assumptions

The label is not checked against a timezone database and a date alone does not resolve an instant.
Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.

Alternative or Complementary methods

Use an authoritative timezone database and complete timestamp context to resolve an actual local time or day.

References

Calculation and input contract: date/date-only-timezone-annotation — tool.io

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