Unix Timestamp Seconds vs Milliseconds
How to tell whether a Unix timestamp is in seconds or milliseconds before converting it.
Count the digits
Modern Unix timestamps in seconds are usually 10 digits. Millisecond timestamps are usually 13 digits because they multiply seconds by 1,000.
Watch for impossible dates
If a date lands in 1970 or far in the future, the value may have been interpreted with the wrong unit. Switch between seconds and milliseconds before assuming the source data is wrong.
Open the related tool and keep the workflow local.