Unix timestamps: seconds, milliseconds, and the date they represent
Read an API timestamp correctly and convert it into an unambiguous UTC date.
A timestamp in an API response may look like an arbitrary long number. Before converting it, find out whether the service means seconds or milliseconds. Guessing from the number of digits is tempting, but it can fail for older dates and unusually large values.
Start at the Unix epoch
Unix time counts elapsed seconds from 1970-01-01 at midnight UTC. The number 1704067200 represents 2024-01-01T00:00:00Z. If the service uses milliseconds, that same instant is 1704067200000. The extra three zeros come from one thousand milliseconds per second, not from a different time zone.
Open the Unix timestamp converter, choose the input format explicitly, and paste the value. It displays an ISO 8601 UTC date along with Unix seconds and milliseconds. If you are entering an ISO date instead, include a Z or a numeric offset such as +01:00. A date and time without an offset cannot identify one global instant by itself.
Why a local clock can show a different hour
A timestamp identifies an instant. Your calendar app may display that instant in your local zone. For example, 12:00Z can appear as 13:00 in a region that is one hour ahead of UTC at that date. Daylight saving rules can change the difference at another date. When troubleshooting a scheduled event, compare the UTC value first and then convert it to the intended local zone.
Check the source contract
Read the API field description for its units. Do not silently divide a large value by 1,000 in production code just because it has thirteen digits. This browser converter is useful for inspection, but it cannot correct a wrong unit supplied by an upstream system. It processes the value locally and does not send it to the site.