tohox If an Internet connexion is available could I synchronize the internal clock on boot using SNTP?
Whenever it connects to the internet it automatically tries to synchronise to a remote server. We didn't do anything specific to obtain that, it's built into Debian somehow (I assume as a systemd service?).
Depending on the use case (i.e.: if you don't need Pd to do anything while waiting for the right time), you can also wrap it all in a bash script:
while sleep 1; do
DATE=$(date '+myformat') #TODO: specify appropriate format
if [ $DATE -ge $MIN_DATE -a $DATE -le $MAX_DATE ] # simple comparison, may be more complex in your case
then
# RUN THE PROGRAM
endif
done
This won't put the board into any sort of low-power mode, but that shouldn't be a problem if you are mains-powered. If you are battery-powered, then an RTC with programmable interrupt is probably the best solution, assuming such a device exists ...