why currentTime() function value is negative value

[Han-WenLIU]

I'm using geoevent to handle real-time data with pull an external website for json 

I create a processor to calculate current using currentTime() function format in Long and put  it in a new geoevent definition

than I use field mapper to map the 'current' into my feature layer so I can see the value of it

but I get the value like this:

if I change the number into date format, I will get a day in 1916 Aug 20 Sunday 18:40:11

is it correct or where am I do wrong?

thanks for your help. 

ps. I am following Mark Bramer 's reply in geoevent filter to ensure a date field is within a tolerance of the current time