About

Unix timestamps represent time as the number of seconds elapsed since 1970-01-01T00:00:00Z (the Unix Epoch). This converter transforms any date into its epoch representation in seconds, critical for database storage, API communications, and cross-timezone calculations where human-readable formats introduce ambiguity. A single timezone miscalculation in financial systems can shift transaction timestamps by 3600 seconds per hour offset, causing audit failures and reconciliation errors.

The duration mode calculates the precise difference between two dates. Unlike naive approximations using 365.25 days per year, this tool computes actual elapsed time accounting for leap years, varying month lengths, and daylight saving transitions. Note: results assume UTC unless your browser interprets local timezone from the input - verify critical timestamps against a reference epoch table.

Formulas

The Unix timestamp conversion extracts milliseconds from the JavaScript Date object and divides by 1000 to obtain seconds:

t_unix = Date(input).getTime()1000

Where t_unix = Unix timestamp in seconds, and getTime() returns milliseconds since epoch.

For duration between two dates:

Δt = |t₂ − t₁|

The unit breakdown follows integer division with modulo extraction:

days = floor(Δt86400)

hours = floor(Δt mod 864003600)

minutes = floor(Δt mod 360060)

seconds = Δt mod 60

Reference Data

Time Unit	Seconds Equivalent	Common Use Case
1 Minute	60	Session timeouts, rate limiting
1 Hour	3,600	Cache expiration, JWT tokens
1 Day	86,400	Daily cron jobs, log rotation
1 Week	604,800	Password reset links, trials
30 Days	2,592,000	Cookie expiration, billing cycles
365 Days	31,536,000	Annual subscriptions, compliance
Leap Year	31,622,400	Accurate multi-year calculations
Unix Epoch Start	0	1970-01-01 00:00:00 UTC
Y2K (2000-01-01)	946,684,800	Historical reference point
32-bit Overflow	2,147,483,647	2038-01-19 03:14:07 UTC (Y2K38)
Current Max Safe	8,640,000,000,000	JavaScript Date limit (~275,760 CE)
1 Millisecond	0.001	High-precision timing, animations
1 Microsecond	0.000001	Performance profiling
1 Nanosecond	0.000000001	Hardware-level timing
Sidereal Day	86,164.1	Astronomical calculations
Mean Solar Day	86,400.002	Civil timekeeping average
Gregorian Year	31,556,952	Average accounting year
Julian Year	31,557,600	Astronomical standard (365.25 days)
Tropical Year	31,556,925.2	Seasonal cycle calculations

Frequently Asked Questions

Your browser interprets datetime-local inputs in your local timezone, then converts to UTC internally. A date entered as 2024-01-15T12:00 in UTC+3 becomes 2024-01-15T09:00 UTC, yielding a timestamp 10,800 seconds lower. Always verify whether your source expects local or UTC time. This tool displays both the raw epoch and your timezone offset for transparency.

Dates before the Unix Epoch produce negative timestamps. For example, 1969-12-31T23:59:00 UTC equals -60 seconds. JavaScript's Date object supports dates from approximately 271,821 BCE to 275,760 CE, though precision degrades for extreme values. Most databases and APIs accept negative Unix timestamps without issue.

32-bit systems store Unix timestamps as signed integers with a maximum value of 2,147,483,647 seconds (2038-01-19T03:14:07 UTC). Beyond this, the value overflows to negative numbers. JavaScript uses 64-bit floats internally, supporting timestamps until approximately year 275,760. This tool operates safely within JavaScript's limits but cannot prevent issues in external 32-bit systems receiving your exported timestamps.

Non-leap years contain 365 days (31,536,000 seconds) while leap years contain 366 days (31,622,400 seconds). When calculating duration between specific dates, the tool uses actual elapsed time rather than averages. A span from 2024-01-01 to 2025-01-01 yields 31,622,400 seconds because 2024 is a leap year.

Yes. Enter the timestamp in the input field and toggle to reverse mode. The tool parses numeric input as seconds since epoch and displays the corresponding UTC date. For millisecond timestamps (13 digits), divide by 1000 first or use the auto-detection which identifies timestamps by digit count.

The tool calculates duration using UTC milliseconds, which are unaffected by DST transitions. A 24-hour civil day spanning a DST change contains either 23 or 25 hours of actual elapsed time. The displayed seconds reflect true elapsed duration, not calendar assumptions. For civil day counting, be aware that 86,400 seconds does not always equal one calendar day in local time.