When departing from an uncontrolled airport, by when must you contact ATC if you haven't departed by clearance void time?

When departing from an uncontrolled airport, it is essential to adhere to the clearance void time specified by air traffic control (ATC). This time indicates the period by which you must commence your flight after receiving your clearance. If you have not departed by the clearance void time, you must contact ATC within 30 minutes. This timeframe allows ATC to manage traffic and ensure safety, as they may have granted your clearance to facilitate their operations and are expecting to hear from you shortly after the void time.

Staying within this 30-minute limit ensures that you remain properly coordinated with ATC and that your intentions are communicated. If you delay beyond this period without notifying ATC, the clearance is considered void, and you would need to obtain a new clearance before departing. This requirement is crucial for maintaining the orderly flow of air traffic, particularly around airports where ATC services are in effect.