Definition
Quiet hours are the times of day when promotional messages may not be sent to recipients, set by regulators, operators or a business's own policy. Transactional messages such as OTPs and alerts are normally exempt.
In the GCC, several regulators publish explicit windows. UAE: TDRA's spam policy bars marketing text messages between 21:00 and 07:00 UAE time. Saudi Arabia: CST's Regulations for Curbing SPAM Messages and Calls ban promotional messages from 22:00 to 09:00, and from 01:00 to 12:00 during Ramadan. Qatar: the CRA's Spam Regulation bars direct-marketing messages between 21:00 and 09:00. Rules change, so confirm the current text with the regulator before scheduling.
Where no regulator window has been published, as in Kuwait and Egypt, agree sending hours with the operator and send promotions in the recipient's local daytime.
Quiet hours apply in the recipient's time zone, not the sender's. A campaign scheduled from Cairo at 20:30 is 22:30 in Dubai in winter (21:30 while Egypt is on summer time), inside the UAE quiet window either way. Large campaigns can also spill into quiet hours if throughput is limited, so schedule them early or split them.
Keep transactional traffic separate (different sender IDs or templates) so that OTPs and alerts are never queued behind marketing rules.
Example
Saudi campaign scheduled 21:45 Riyadh time with 40 minutes of sending: the tail end would pass 22:00 — reschedule to start at 10:00 next morning.