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1735689600

Unix Timestamp Converter

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Convert Unix timestamps to human-readable dates and back — auto-detects seconds vs milliseconds, supports UTC offsets, and shows relative time.

sec & ms
Bidirectional
Instant
Private
Unix Timestamps
1735689600
Seconds (Unix timestamp)
1735689600000
Milliseconds
Formatted
2025-01-01T00:00:00.000Z
ISO 8601
Wednesday, 1 Jan 2025 00:00:00 UTC
UTC string
Wednesday, 1 Jan 2025 00:00:00 UTC
Local string
1 Jan 2025
Short date
Wednesday, 1 January 2025 at 00:00:00 UTC
Long date
00:00:00
Time only
Wed
Day
1 Jan 2025
Date
00:00
Time
W1
Week
Relative time
2 years ago

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How to Use

  1. 1 Choose mode: Timestamp → Date (paste a Unix timestamp), Date → Timestamp (paste a date string), or Current (see the current timestamp)
  2. 2 Paste or type a Unix timestamp (seconds or milliseconds — auto-detected)
  3. 3 Or paste an ISO 8601 date string like '2025-01-01T00:00:00Z' to get the timestamp
  4. 4 Set a UTC offset if you want the local time displayed in a specific timezone
  5. 5 Copy the result: Unix seconds, milliseconds, ISO string, UTC string, or local string

Features

  • Auto-detects seconds vs milliseconds: values below 10^10 treated as seconds, above as milliseconds
  • Bidirectional: timestamp to date and date string to timestamp
  • UTC offset support — apply any half-hour or full-hour offset (e.g. +5.5 for IST)
  • ISO 8601, UTC string, and local string outputs with day-of-week and week number
  • Human-relative time: '3 days ago', 'in 2 hours', 'in 1 year'
  • Current timestamp mode shows live Unix time in both seconds and milliseconds

Why it Matters

Unix timestamps are the universal language of time for software systems — databases, APIs, log files, and distributed systems all store times as seconds or milliseconds since the Unix epoch (1 January 1970 00:00:00 UTC). Converting between this integer and a human-readable date is a daily task for developers, data analysts, and anyone working with API responses or server logs. Knowing whether a timestamp is in seconds or milliseconds is a common point of confusion — this converter handles both automatically.

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Use Cases

API Debugging

Decode created_at, updated_at, and expires_at timestamps from JSON API responses instantly

Log Analysis

Convert Unix timestamps in server access logs or database records to readable dates for filtering

Date Arithmetic

Get the Unix timestamp for a target date so you can compare or difference with other timestamps in code

Data Engineering

Validate that epoch values in a data pipeline fall within expected date ranges

The Unix epoch

The Unix epoch is midnight UTC on 1 January 1970. Every Unix timestamp is simply the count of seconds (or milliseconds) since that instant. Because the count is a plain integer, comparing, storing, and doing arithmetic with timestamps is trivially simple — no timezone offsets, no daylight saving rules, no calendar ambiguity.

Seconds vs milliseconds

JavaScript’s Date.now() returns milliseconds (13 digits). Most Unix utilities, databases, and POSIX APIs work in seconds (10 digits). The ambiguity causes subtle bugs — a timestamp of 1735689600 is 1 January 2025, but 1735689600000 is the same instant in milliseconds. The converter auto-detects which you have.

Privacy

All conversions happen in your browser. No timestamps or dates are sent to any server.

Frequently Asked Questions

What is a Unix timestamp?
A Unix timestamp is the number of seconds (or milliseconds) that have elapsed since the Unix epoch: 00:00:00 UTC on 1 January 1970. It is a single integer that uniquely identifies any point in time, making it ideal for storage, comparison, and arithmetic in software systems. The current Unix timestamp in seconds is a 10-digit number (around 1.7 billion as of 2024).
How do I tell if a timestamp is in seconds or milliseconds?
Timestamps in seconds are currently about 10 digits long (e.g. 1735689600). Timestamps in milliseconds are 13 digits long (e.g. 1735689600000). This converter auto-detects: values below 10,000,000,000 (10^10) are treated as seconds; values above that are treated as milliseconds.
What is the Unix epoch and why does it start in 1970?
The Unix epoch — 1 January 1970 — was chosen by the designers of Unix as a convenient starting point. It predates most modern computing, so practical timestamps are always positive. The choice was somewhat arbitrary but has become universal. The standard is formally defined in POSIX.
What is the Year 2038 problem?
32-bit signed integers can store values up to 2,147,483,647, which corresponds to 19 January 2038 at 03:14:07 UTC. Systems that store Unix timestamps in a 32-bit integer will overflow on this date. Modern systems use 64-bit integers, which can represent dates billions of years in the future.
What is ISO 8601 and how is it different from Unix time?
ISO 8601 is a human-readable date format standard, e.g. '2025-01-01T12:00:00Z'. Unix time is a machine-friendly integer. Both represent the same instant but serve different purposes — ISO 8601 is for display and data interchange, Unix time is for storage and arithmetic. This converter handles both as input and output.
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