Milliseconds to Date Converter

Convert milliseconds timestamps to human-readable dates with auto-detection.

Timestamp (seconds or milliseconds)

Enter a Unix timestamp to convert milliseconds to date. The tool auto-detects whether your input is in seconds or milliseconds based on its magnitude.

Understanding Milliseconds vs Seconds Timestamps

Unix timestamps measure time as the number of time units since January 1, 1970 00:00:00 UTC (the Unix epoch). The two most common units are:

Seconds (10 digits)

1700000000

Used by: Unix/Linux systems, PHP, Python, Ruby, most backend languages, POSIX timestamps

Milliseconds (13 digits)

1700000000000

Used by: JavaScript (Date.now()), Java (System.currentTimeMillis()), databases like MongoDB, browser APIs

Common Bug Alert

Mixing up seconds and milliseconds is one of the most common timestamp bugs. If your date shows up as 1970 (near the epoch) or far in the future (year 50000+), you probably have a unit mismatch. A milliseconds timestamp used as seconds will be 1000x too small; a seconds timestamp used as milliseconds will be 1000x too large.

Quick Detection Rules

10 digits or fewer = almost certainly seconds
13 digits or more = almost certainly milliseconds
11-12 digits = ambiguous zone (rare) - verify the expected date range
Decimal point = seconds with fractional precision (e.g., 1700000000.123)