Puck.js as power meter logger - how do you keep track of pulses per hour and day?

Hi
I have started with this example as a base to modify for my needs:
https://www.espruino.com/Smart+Meter

I am measuring time between pulses to calculate current power use. But I also want to keep track of pulses per hour and per day. I am lost at math that is used in the example to modify. I dont need an array to store, as data will be picked up but another device and stored elsewhere.
Can someone point me in the right direction/assist with javascript to detect a day/hour rollover, so that counters can be reset?
Some pseudo-code =)

var hourPulses=0
var dayPulses=0
For every pulse
   if hour > previous hour then hourPulses =0
   if day > previous day then dayPulses =0
   increment dayPulses
   increment hourPulses
   send NRF data
   loop

Something like that. I just dont know how it will work when moving into a next day.
The example in the link above somehow magically sets it into an array. But I just want one value to be sent for the current hour and day.