Seconds or milliseconds
Formalint detects common Unix seconds and Unix milliseconds values and shows both forms in the output.
Browser-based developer tools
Timestamp Converter
Convert Unix timestamps, milliseconds and ISO dates into UTC and local browser time.
Reference notes
Unix time without mental math
UTC and local
UTC output is useful for logs and APIs, while local browser time helps compare what users actually see.
ISO input
Paste an ISO date string to convert it back into Unix timestamp values for tests, fixtures and API requests.
Frequently asked
Timestamp converter questions
What is the difference between Unix seconds and milliseconds?
Unix time in seconds is a 10-digit number for current dates, while JavaScript and many APIs use milliseconds, a 13-digit number. Pasting a 13-digit value as seconds gives a date far in the future.
Does the converter account for time zones?
Unix timestamps are always UTC-based. The tool displays both the UTC value and your browser's local time zone so you can compare the two directly.
What ISO 8601 formats are supported?
Standard ISO date strings including date-only, date-time with a Z suffix for UTC, and date-time with an explicit offset such as +03:00 are all parsed correctly.