Practical usage guide
What this tool does
Unix time counts elapsed seconds from 1970-01-01 00:00:00 UTC. Many browser and API systems use milliseconds instead, which produces values roughly one thousand times larger. This converter accepts one value per line and can display UTC, browser-local, or an IANA timezone.
A timestamp identifies an instant, while a formatted date adds a timezone and calendar representation. The same instant can therefore appear as different local dates in different regions without the timestamp changing.
Quick start
Enter one value per line
Mix numeric timestamps and parseable date strings for quick checks. Use an explicit input unit when you already know whether numbers are seconds or milliseconds.
Choose the display timezone
Use UTC for system logs, Local for your browser timezone, or Custom with an IANA name such as Asia/Shanghai or America/New_York.
Compare the numeric and ISO forms
Review Unix seconds, Unix milliseconds, UTC ISO output, and the selected-zone display before copying a result.
Common use cases
Decode log and event times
Translate epoch values from databases, analytics, or queue messages into readable dates.
Prepare API time fields
Convert a planned date to seconds or milliseconds according to an API contract.
Check cross-region schedules
View the same instant in UTC and a named timezone to catch date-boundary or daylight-saving surprises.
Limitations and important notes
Auto unit detection uses a numeric threshold
Absolute values below 100,000,000,000 are treated as seconds; larger values are treated as milliseconds. Select the unit manually for unusual historical or future values.
Date strings without a timezone are ambiguous
Browser parsing can interpret an offset-free date in the local timezone. Prefer ISO 8601 with Z or an explicit offset for reproducible results.
Daylight-saving transitions can repeat or skip local times
A named timezone may have offset changes. Store instants as UTC timestamps and use local formatting only for display.