Get + Set
Day.js uses overloaded getters and setters, that is to say, calling these methods without parameters acts as a getter, and calling them with a parameter acts as a setter.
As dayjs objects are immutable, all setters will return a new dayjs instance.
These map to the corresponding function on the native Date object.
dayjs().second(30).valueOf() // => new Date().setSeconds(30)
dayjs().second() // => new Date().getSeconds()
If you are in UTC mode, they will map to the UTC equivalent.
dayjs.utc().second(30).valueOf()// => new Date().setUTCSeconds(30)
dayjs.utc().second()// => new Date().getUTCSeconds()