Does this accept a numeric offset without a colon, like -0400?

Yes, both -04:00 and -0400 are valid ISO 8601 offset forms, and either is detected correctly as a present offset.

What does floating mean here?

A floating timestamp states a calendar date and, optionally, a wall clock time, with no attached time zone. The same floating string can name a different real instant depending on which zone eventually gets attached to it.

ISO 8601 Timestamp Inspector

Paste a raw ISO 8601 timestamp to see exactly what it says. This reports the detected precision, whether an offset or Z suffix is present, and the normalized instant when one can be computed. A timestamp with no offset is not treated as an error. It is a valid floating local timestamp under the ISO 8601 grammar.

Need to convert this into an epoch value instead? See Unix Timestamp Converter.

Worked example

The string 2027-03-14T09:30:00-04:00 carries an explicit offset of four hours behind UTC, so it names one real, unambiguous instant on the universal timeline, detected here at second precision. The bare date 2027-03-14, with no time portion at all, is day precision with no offset, which is a perfectly valid ISO 8601 date, just not one that can be resolved to a specific instant on its own. Add fractional seconds such as 2027-03-14T09:30:00.123Z and the inspector reports millisecond precision along with the Z suffix, which stands for Zulu time, meaning UTC with a zero offset.

Common mistakes

Treating a timestamp with no offset as if it were secretly UTC. ISO 8601 makes no such assumption, and neither does this tool. A floating timestamp needs an explicit time zone from somewhere else before it can be converted to a real instant.
Assuming every fractional second length means the same precision tier. Millisecond, microsecond, and nanosecond precision are each detected separately based on how many digits actually follow the decimal point.

Limitations

This inspects syntax and structure only. It does not verify that a timestamp came from any specific system, log file, or API, and it makes no claim about which time zone a floating timestamp was originally intended to represent. Pair a floating result with the actual known source system's zone before treating it as a real instant.

Frequently asked questions

Does this accept a numeric offset without a colon, like -0400?: Yes, both -04:00 and -0400 are valid ISO 8601 offset forms, and either is detected correctly as a present offset.
What does floating mean here?: A floating timestamp states a calendar date and, optionally, a wall clock time, with no attached time zone. The same floating string can name a different real instant depending on which zone eventually gets attached to it.