Description
Return the UTC interval corresponding to a local date at a fixed offset.
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.
Return the UTC interval corresponding to a local date at a fixed offset.
When to use this tool
Use Local Date Fixed Offset Preimage when inspecting a supplied offset or timezone annotation.
How to use the tool and how it works
- Enter localDate, offsetMinutes. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read lowerUtc, upperUtcExclusive. Use the output convention below.
Return the UTC interval corresponding to a local date at a fixed offset. Validate date and whole offsetMinutes in [-1439,1439]; subtract offset from local midnight and return that UTC instant plus exactly 86400000 milliseconds as the exclusive end.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| localDate | Local Date | Required. Text; maximum UTF-16 length 8192. Real proleptic Gregorian YYYY-MM-DD; four-digit years 0000-9999 accepted. |
| offsetMinutes | Fixed signed UTC offset in minutes; not a time-zone identifier or daylight-saving rule. | Required. Safe integer; minimum -1439; maximum 1439. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| lowerUtc | UTC instant for local midnight under the supplied fixed offset. | Required. Text; maximum UTF-16 length 8192. |
| upperUtcExclusive | UTC end of the fixed 24-hour interval, excluded. | Required. Text; maximum UTF-16 length 8192. |
{
"input": {
"localDate": "2026-10-26",
"offsetMinutes": 120
},
"output": {
"lowerUtc": "2026-10-25T22:00:00.000Z",
"upperUtcExclusive": "2026-10-26T22:00:00.000Z"
}
}Limitations and assumptions
- This fixed-offset day ignores DST and timezone transitions; it is not a general zoned-day resolver.
- 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
Similar or alternative tools
- Date: Timestamp Offset Negative Zero Check
Distinguish known zero UTC offset from unknown local offset.
- Timestamp Offset Second Component Token
Parse a signed offset including seconds.