When Funnel retrieves data from the sources you have connected, the data is attributed to calendar days. The definition of day for each source will be depending on the originating platform and your settings there.
I.e. if you set up your Facebook Ad Accounts to use Pacific Standard Time (PST) the definition of "January 1 2018" for those sources will be according to the PST time zone. Funnel can not "convert" between time zones.
It's also worth noting for data collection that the previous "day" of data is very rarely complete at the source early in the next day, and in many cases the data will keep changing for up to 30 days.
Data Warehouse Exports
As you configure, edit or just browse one of your Data Warehouse exports in Funnel you will likely come across the schedule time for it. This time is presented differently depending on where you are in the world. In my case, it will look like this:
Funnel detects time as an offset from the current UTC time (your local time can be expressed as UTC plus/minus a set integer) which is given your browser. This does not account for Daylight Savings, i.e any export time will be stored in UTC, but expressed in your local time using the offset returned by your browser at the time of viewing your export.
So, in Sweden, my browser returns the time in UTC+2 during Central European Summer Time, but in UTC+1 the rest of the year. If you are at Eastern Daylight Time (EDT) in the US, the equivalent would be UTC-4, but for the duration when EST applies that would be equivalent to UTC-5 instead.
As an example, if I set my Funnel export to run at 09.00 AM UTC+2 while in my local Daylight Savings time, it will actually be expressed as being 08.00 AM UTC+1 when Daylight Savings is no longer applicable. This is caused by my local offset from UTC changing from +2 to +1. Under the hood, though, the actual time that the export is run is 07.00 AM UTC!