How do I set one posting time for all campaigns?

Use the card Posting time — all campaigns on AI AutoPost → Auto Setup. It applies to every campaign on your site, not only the ones Auto Setup made. You have three choices:

• Each campaign uses its own schedule – the default; each campaign follows its own Update Frequency.
• Every N minutes / hours / days – for example every 2 hours. Every campaign tries to add one new post each time, and each campaign still uses its own Start Time.
• At fixed times every day – type 24-hour times separated by commas, for example 09:00, 13:00, 18:00. With 3 times and 5 campaigns you get about 15 posts a day. Start Time is not used in this mode.

All times use your site time zone from Settings → General → Timezone. If the times are empty or typed wrongly, the page falls back to each campaign using its own schedule. When a global time is active, the Update Frequency box of every campaign shows a blue note with a Change link. Save the page to apply it.