This question already has an answer here:

I work on a project that date and time is very important. I want force raspberry to sync time with a ntp server and if time not sync raspberry won't boot or wait for time sync and after succeed resume boot. How can I do it?

marked as duplicate by Ghanima, goldilocks Feb 17 '15 at 10:16

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Browse other questions tagged or ask your own question.