Unix timestamp

Unix time counts whole seconds since the Unix epoch: 1970-01-01 00:00:00 UTC. Developers encounter epoch values in logs, JWT exp claims, database columns, and API payloads. This converter decodes seconds into readable civil datetime and encodes calendar input back into epoch form so you can debug timestamps without guessing time zones or leap-second policy.

When to use a Unix timestamp converter

Reach for this page when a log line shows ten digits like 1735689600 and you need the corresponding calendar moment. SRE teams decode alert thresholds. Mobile engineers compare server exp fields with device clocks. Data analysts join CSV exports where one column is epoch seconds. For dozens of values, use the batch timestamp converter. Hexadecimal encodings belong on the hex timestamp converter.

Windows LDAP and FILETIME integers belong on the LDAP timestamp page — different epoch and unit scale entirely.

How Unix epoch seconds work

The epoch is not a timezone; it is a fixed instant. Each increment adds one SI second in the Unix convention, which ignores leap seconds for most software stacks. Libraries map known anchors regardless of whether a leap second occurred that year. Negative values represent instants before 1970, still appearing in legacy financial and scientific datasets.

Millisecond timestamps append three digits. Divide millisecond fields by 1000 before pasting when your source stores ms. Nanosecond logs from some languages need similar scaling down to whole seconds for this UI.

Accuracy, time zones, and display

Decoding is exact for integers your engine supports. Display shifts when you choose a local offset: the underlying instant stays the same while the printed clock time moves. Daylight saving transitions can make two different local times map to the same offset on spring-forward days — note whether your pipeline stores UTC or local civil time.

For legal deadlines tied to a city, pair epoch decoding with the time zone hub rather than assuming UTC. For scheduling relative to today, the days until calculator handles civil dates without epoch math.

Worked examples

Example A: an API returns exp=1735689600 in a JWT. Decode here to see token expiry in UTC, then compare with your laptop clock. If it reads one hour early, check whether the API documents UTC while you read local time.

Example B: seed a database with midnight UTC on the first day of 2026. Encode that calendar date, copy the epoch integer into your INSERT script, and round-trip decode once to confirm. Cross-check with the ISO 8601 converter if the column expects strings.

Example C: a partner sends seconds since epoch for analytics events. Pick three known holidays from the 2026 holidays list and verify decoded dates before importing millions of rows.

Common pitfalls

Mixing seconds and milliseconds is the top support issue — count digits. Treating epoch as local midnight without converting causes off-by-one-day bugs near the International Date Line. Storing floating-point seconds loses precision beyond 2^53 — use integers in JSON.

Excel serial dates and Unix seconds are unrelated numbering systems. UUID version 1 timestamps embed a different 100-ns clock — see UUID timestamp when the input is a UUID string, not bare digits.

Database and API conventions

PostgreSQL to_timestamp and MySQL FROM_UNIXTIME expect seconds in most schemas, while JavaScript Date.now returns milliseconds. Redis EXPIRE uses relative TTL, but session blobs often store absolute exp as epoch integers. GraphQL createdAt fields may be ISO strings while legacy REST endpoints still return ten-digit numbers — normalize at the service boundary before joining datasets.

When designing new tables for 2026 services, prefer timestamptz or ISO text over bare integers so future migrations touch fewer columns. Document whether your OpenAPI schema types time as integer or string for partner integrations.

JWT, cookies, and session expiry

JSON Web Token exp claims are NumericDate values in seconds. Decoding here compares token lifetime with server clock skew budgets. Remember that exp is a hard cutoff — refresh flows should trigger before the decoded instant, not after.

Browser cookies use Max-Age in seconds from issuance, not epoch, but server-side session stores often persist absolute expiry as epoch for sweep jobs. Align cron cleanup with decoded UTC instants using the cron calculator when batch-deleting rows.

Logging and observability

Structured logs often serialize timestamps in ISO while legacy apps emit epoch in message text. Normalize both to the same instant before building SLO dashboards. When log shipping lag equals one bucket width, do not confuse ingestion delay with clock drift.

Trace spans may record startTime in microseconds since epoch — scale down before using this page. Align span ids with external ticket timestamps by converting in the timezone documented in your runbook.

Mobile and embedded timestamps

iOS NSDate and Android epoch helpers return different precisions — always read platform docs before comparing with server ten-digit fields. Embedded devices without NTP may drift minutes; decode here then compare with SNTP-corrected server logs during field debugging.

Offline-first apps queue events with local epoch at capture time and reconcile on sync — document whether merge logic uses client or server clock when both appear in support tickets.

Historical and pre-1970 datasets

Negative Unix seconds represent instants before 1970 still present in legacy financial series and scientific archives. Genealogy tools importing mainframe extracts should verify sign before charting — a negative decode is valid history, not a parse error.

When teaching 2026 CS courses, contrast Unix epoch with FILETIME and UUID clocks so students map the right converter to each log column without habit defaulting to ten-digit only.

Certificate and API expiry audits

Annual TLS inventory spreadsheets list notAfter as epoch in some exports — decode sample rows before sorting ascending for 2026 renewal queue. Partner webhooks documenting retry windows in seconds decode here for on-call runbooks written in civil time.

Related tools

Explore the converters hub for batch and hex epoch tools, LDAP/FILETIME, and ISO strings. Civil date math without epochs lives on date tools. Clocks and duration timers: time tools.