Time format in Data time series node

When using time series node and aggregation Mean, the time value is a unix timestamp, but when using Sum, it a character string.
Is there a reason for that?
If not how do best format the time value in preparation for a CSV encode node?

@Lars_Andersson,

Can you provide some screenshots of what you’re seeing? As always, the more information you can provide the better.

I misspoke. It’s when I run the payload through the CSV encode node that the date-time string gets converted to a unix time stamp. (Changing from mean to sum was not the problem)
before:
image
after:


how would I best be able to keep the string format?

Do I need to convert the time to a string before using the CSV Encode Node?