Unix Timestamp Column to ISO Datetime

Convert integer Unix timestamp cells in explicit seconds or milliseconds to UTC ISO datetimes with millisecond precision, limited to years 0001 through 9999.

Description

Unix timestamps measure elapsed time from the UTC epoch.

Unix timestamps measure elapsed time from the UTC epoch. Explicit seconds versus milliseconds avoids an ambiguous scale when converting spreadsheet cells.^[1]

Convert integer Unix timestamp cells in explicit seconds or milliseconds to UTC ISO datetimes with millisecond precision, limited to years 0001 through 9999.

When to use Unix Timestamp Column to ISO Datetime

Use this for the following task: Convert integer Unix timestamp cells in explicit seconds or milliseconds to UTC ISO datetimes with millisecond precision, limited to years 0001 through 9999.

Prepare the CSV text, decoded cells or byte values requested below. Choose delimiter and header flags explicitly when those fields are present.

How to use Unix Timestamp Column to ISO Datetime and understand its results

Prepare the CSV text, decoded cells or byte values requested below. Choose delimiter and header flags explicitly when those fields are present.
Enter values, unit using the field table, then run the tool.
Read isoDatetimes. Interpret flags, units, ordering and placeholder values using the rules below.
Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.

Input field	Meaning	Value type and bounds	Requirement
values	Values	list of string; minimum entries 0; maximum entries 10000; each entry: string; maximum text length 30	Required
unit	Unit	string; choose "seconds", "milliseconds"	Required

Trim and validate signed integer cell text, convert with exact integer arithmetic, and require the resulting date within years 0001–9999. Emit UTC ISO strings with millisecond precision.^[2]

milliseconds = integer cell × (1000 for seconds, 1 for milliseconds)

This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.

Output field	Meaning	Value type
isoDatetimes	Iso datetimes	list of string

json

{
  "input": {
    "values": [
      "0",
      "1704067200"
    ],
    "unit": "seconds"
  },
  "output": {
    "isoDatetimes": [
      "1970-01-01T00:00:00.000Z",
      "2024-01-01T00:00:00.000Z"
    ]
  }
}

Limitations and assumptions

Fractional/exponent spellings are rejected. No local timezone or guessed timestamp unit is used.

Supply the decoded cell strings or raw values declared by the input fields; this tool does not load a spreadsheet file. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.

Alternative or Complementary methods

Choose Two-Digit Year Century Window Rule Lookup for this operation: Resolve a two-digit year into a caller-specified inclusive 100-year window, returning the unique year with matching final digits; no operating-system date setting is assumed. For a complementary task, use Mixed-Type Column Detector Samples for this operation: Report observed nonblank ASCII token classes per CSV data column and whether more than one occurs; integer and decimal spellings are distinct classes even when inference can promote both to decimal.

Further background: Format and language reference: Unix Timestamp Column to ISO Datetime.

References

Format and language reference: Unix Timestamp Column to ISO Datetime — Ecma International / TC39
Unix Timestamp Column to ISO Datetime — tool.io

Similar or alternative tools

Two-Digit Year Century Window Rule Lookup
Resolve a two-digit year into a caller-specified inclusive 100-year window, returning the unique year with matching final digits; no operating-system date setting is assumed.
Mixed-Type Column Detector Samples
Report observed nonblank ASCII token classes per CSV data column and whether more than one occurs; integer and decimal spellings are distinct classes even when inference can promote both to decimal.