Millisecond in timestamp

Hi,

Is there any way we can get millisecond in timestamp? I realize there’s date() & time() function, but I guess it’s only give second as the smallest unit if I’m not wrong

I use this

http://devwiki.electricimp.com/doku.php?id=electricimpapi:hardware

hardware.millis() – free-running millisecond ticker

do you append it to the timestamp or just use it as a millisecond timer?
I need the millisecond as part of the timestamp. Perhaps I need to do this manually?

When I do something; like take a new temperature reading for process control, I save the current value

in this snippet, I calculate the slope of a temperature rise. After using the timestamp, set tmprevious equal to it so I can use that the next time through the
loop

tmstamp = hardware.millis();

slope=(currenttemp-oldtemp)/(tmstamp-tmprevious);

tmprevious=tmstamp;

the counter just keeps going up and so you would need to consider what happens when it wraps

thanks for the reply
I get the timestamp of first the data was logged and the millis difference for each of the data