UNIX Time Converter
Convert UNIX timestamps (seconds or milliseconds) to UTC/local time and back.
The tool auto-detects whether the input is 10-digit seconds or 13-digit milliseconds
and updates all fields in real time with no API calls.
View ISO 8601 output, human-readable strings, and the detected weekday.
Quick actions let you copy any field, jump to the current time, auto-refresh every second, or clear inputs.
All calculations are done in your browser using the native Date and Intl APIs.
Auto-detects seconds or milliseconds
Auto-syncs with UNIX input. Accepts local time.
Unix Timestamp Converter
Unix timestamps appear in logs, databases, API responses, JWT claims, analytics exports, and monitoring alerts. This converter turns second-based or millisecond-based timestamps into readable dates and helps you convert dates back into timestamp values.
Common use cases
- Debug logs: Convert raw timestamps into human-readable times during incident investigation.
- Check API fields: Review
created_at,updated_at,iat,exp, and expiration values. - Validate stored data: Confirm whether database timestamps match expected user actions or system events.
Seconds vs milliseconds
A 10-digit timestamp is often seconds, while a 13-digit timestamp is often milliseconds, but systems vary. If the resulting date looks far in the past or future, check whether you are using the correct unit.
Articles for this tool
Unix Time and Timezones: A Practical Engineering Reference
Master Unix timestamps — what they are, the seconds vs milliseconds trap, timezone handling in JavaScript, Python, Go, and SQL, the 2038 problem, and how to convert them reliably.
How to Convert Milliseconds, Seconds, Minutes, and Hours for Timeouts and TTLs
Convert time units for API timeouts, cache TTLs, retry delays, polling intervals, and monitoring settings without mixing up milliseconds and seconds.
UTC to JST Reference: The 9-Hour Offset, Cheat Sheet & Timezone Pitfalls
Convert between UTC and JST (Japan Standard Time) with a cheat sheet. Covers what Z and +09:00 mean in ISO 8601, when JavaScript date parsing silently shifts by 9 hours, MySQL/PostgreSQL timezone behavior, and why GitHub Actions cron always runs in UTC.
Recent Articles
curl Options Cheat Sheet: What -X, -H and -d Actually Do
A reference for the curl options you meet in real API work: why -d already implies POST, how -d differs from --data-raw, the @ prefix that silently reads a file, single vs double quotes, and why -k and -L deserve more caution than they usually get.
Converting Between JSON Schema and Zod: How required Maps to .optional()
Inside a two-way converter that turns JSON Schema into a Zod schema and Zod code back into JSON Schema. Covers the inverted defaults between required and .optional(), the constraint mapping table, and how the Zod side is parsed without executing any code.
SQL Clause Order Reference: Why WHERE Can't See Your SELECT Alias
The order you write SQL clauses is not the order the database runs them. A reference for the logical execution order (FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT), why aliases fail in WHERE, when to use WHERE vs HAVING, and the MySQL/PostgreSQL differences that bite.
Unified Diff Format Reference: Reading @@ Hunks in git diff Output
How to read the unified diff format git produces: what the four numbers in @@ -12,7 +12,9 @@ mean, why a one-character edit shows as a whole-line replacement, the whitespace and line-ending traps, \ No newline at end of file, combined @@@ diffs on merges, and rename detection via similarity index.
UTC to JST Reference: The 9-Hour Offset, Cheat Sheet & Timezone Pitfalls
Convert between UTC and JST (Japan Standard Time) with a cheat sheet. Covers what Z and +09:00 mean in ISO 8601, when JavaScript date parsing silently shifts by 9 hours, MySQL/PostgreSQL timezone behavior, and why GitHub Actions cron always runs in UTC.
CREATE TABLE Reference: MySQL vs PostgreSQL vs SQLite Types & Constraints
A cross-database CREATE TABLE (DDL) reference with cheat sheets for data types, auto-increment keys (AUTO_INCREMENT / IDENTITY / rowid), foreign key ON DELETE behavior, and the CHECK constraint that MySQL silently ignores.