Civil Time Two Offset Order Reversal Tool

Description

Compare local and fixed-offset UTC order of two minute coordinates.

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.

Compare local and fixed-offset UTC order of two minute coordinates.

When to use this tool

Use Civil Time Two Offset Order Reversal when inspecting a supplied offset or timezone annotation.

How to use the tool and how it works

Enter firstLocalMinute, secondLocalMinute, firstOffset, secondOffset. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read localOrder, utcOrder, reversed. Inspect reversed before interpreting the associated values.

Compare local and fixed-offset UTC order of two minute coordinates. Require whole offsets in [-1439,1439]; subtract offsets to derive UTC order; reversed means localOrder*utcOrder < 0.^[1]

Input field	Meaning and units	Accepted input
firstLocalMinute	First Local Minute	Required. Safe integer.
secondLocalMinute	Second Local Minute	Required. Safe integer.
firstOffset	First Offset	Required. Safe integer; minimum -1439; maximum 1439.
secondOffset	Second Offset	Required. Safe integer; minimum -1439; maximum 1439.

Output field	Interpretation	Returned shape
localOrder	Local Order	Required. Safe integer.
utcOrder	Utc Order	Required. Safe integer.
reversed	Reversed	Required. Boolean.

json

{
  "input": {
    "firstLocalMinute": 600,
    "secondLocalMinute": 630,
    "firstOffset": 0,
    "secondOffset": 120
  },
  "output": {
    "localOrder": 1,
    "utcOrder": -1,
    "reversed": true
  }
}

Limitations and assumptions

Ties are not reversals; location-specific zones and daylight-saving ambiguities are not resolved.
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.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

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/civil-time-two-offset-order-reversal — tool.io

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