How to work with timespans in webSQL

I try to check a time range between 2 dates.

WebSQL can execute this statement 

addMonths(getDate(),5) - getDate()

with the result "153.00:00:00"

If I use Len,substring or other string functions on this result it won´t work. If I use a format before string functions just work fine.

This leads to the conclusion that this result is something of type timespan and not a string. But I can´t find any documentation how to handle time spans in webSql.

I want to get the date-part of thisspan -> 153.

I´m aware that I can use the format function and then just parse it as a text. Just want to know if there is some way to use this time span type.

Thank you.