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How to convert timestamps

Switch between Unix time and readable dates.

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# How to convert timestamps

Timestamp conversion is a daily requirement in analytics, debugging, monitoring, and support. Logs often store Unix timestamps, while humans need readable date-time values with timezone context. A wrong conversion can send teams chasing false incidents or publishing incorrect reports.

This guide explains a reliable conversion workflow between Unix timestamps and human-readable dates, with practical checks to avoid common timezone and unit mistakes.

Understand timestamp units before converting

Most conversion errors come from one issue: mixing seconds and milliseconds.

  • Seconds example: `1717430400`
  • Milliseconds example: `1717430400000`

Quick rule:

  • 10 digits is usually seconds.
  • 13 digits is usually milliseconds.

Always validate unit before any interpretation.

Choose the timezone context first

A timestamp represents a precise moment, but display depends on timezone.

Decide upfront:

  • UTC for system-level analysis
  • Local timezone for business reports
  • User timezone for UI output

If timezone is not fixed in advance, two correct conversions may still look contradictory.

Step-by-step conversion workflow

1. Identify source format

Determine whether input is:

  • Unix seconds
  • Unix milliseconds
  • ISO 8601 datetime string
  • Custom date format with timezone offset

2. Normalize the value

If input comes from logs or spreadsheets, clean formatting first:

  • Trim spaces
  • Remove accidental separators
  • Keep one value per line for batch checks

Useful tools:

3. Convert with explicit options

Use conversion tools with clear mode selection.

Primary tools:

Set these options intentionally:

  • Input unit (sec/ms)
  • Output timezone
  • Output format pattern

4. Cross-check with a second method

For production incidents, verify conversion using at least one extra check.

Helpful tools:

5. Document conversion assumptions

Store assumptions with the result:

  • "Input was Unix milliseconds"
  • "Output displayed in UTC"
  • "Formatting pattern: YYYY-MM-DD HH:mm:ss"

This prevents confusion when results are reused in dashboards or tickets.

Practical examples

Example A: Incident log timestamp

Input

1717430400000

Interpretation

  • 13 digits -> milliseconds

Output goal

  • UTC datetime for postmortem

Result format

2024-06-03 00:00:00 UTC

Example B: API payload in seconds

Input

1717430400

Goal

  • Convert to local support timezone for customer call timeline

Workflow

1. Convert seconds to readable datetime

2. Apply timezone conversion

3. Validate by checking event order

Example C: Schedule generation from calendar date

Sometimes you need reverse conversion: date -> timestamp.

Input

2026-02-14 09:30:00 America/New_York

Output

  • Unix timestamp for scheduling API

Validate daylight saving behavior for that date before publishing automation.

Related tools for date-time workflows

Common mistakes

1. Confusing seconds and milliseconds

This causes dates decades away from reality.

2. Ignoring timezone metadata

Two teams compare UTC and local times as if they were the same.

3. Assuming server timezone equals user timezone

Support and product views can diverge.

4. Formatting without preserving timezone context

A readable date with no timezone label is ambiguous.

5. Skipping daylight saving checks

Offset changes can shift event interpretation by one hour.

6. Batch conversion without input validation

A single malformed value can break downstream reports.

Privacy notes (in-browser processing)

Timestamps may look harmless, but they can reveal sensitive behavior patterns when combined with user IDs, IP events, or transaction references. In-browser conversion reduces the need to send raw logs to third-party systems.

Best practices:

  • Remove user identifiers before sharing conversion samples.
  • Keep raw logs in controlled internal systems.
  • Export only transformed values needed for reporting.
  • Use UTC for internal system analysis, then render local time in user-facing views.

Quick troubleshooting guide

If results look wrong:

1. Check digit length (10 vs 13).

2. Confirm input timezone assumption.

3. Confirm output timezone setting.

4. Verify format token order.

5. Test one known reference timestamp.

A 2-minute validation loop can prevent long debugging detours.

Final checklist

Before using converted timestamps in production:

  • Input unit confirmed.
  • Timezone selected intentionally.
  • Conversion cross-checked with a second method.
  • Output format documented.
  • Sensitive log context handled locally.

Reliable timestamp conversion is not complicated, but it requires discipline. Consistent rules are what keep analytics, alerts, and support timelines trustworthy.