Hi there,
As @msfujino indicates use the delay or the Sleep is the Zyphur using the RTC in System on sleep.
My .02 after scanning some old threads, in anticipation of the Xiao that uses battery like a “Camel in the Desert.” 
When it Drops, Ninja’s will be get’tin “Sturdy” 
Xiao4Ever 
GL 
PJ 