Which is the best way to store dates

Which is the best way to store datetime? is it epoch? is better for indexes? or YYYY-MM-DD HH:mm:ss is the same?

thanks

ISO-8601 format allows to store timezone and also string comparable. N1QL have the following date time functions.
https://developer.couchbase.com/documentation/server/current/n1ql/n1ql-language-reference/datefun.html

epoch will be number it may be faster to compare.