A good maintenance notice answers four questions: when, how long, what breaks, and what you need to do (usually nothing). Send it at least 3 business days ahead for anything customer-visible, and again ~1 hour before you start.
The announcement
Scheduled maintenance: [system], [date]
We'll be performing maintenance on [system] on [date] from [start]–[end] [timezone] ([duration]).
What to expect: [the honest impact — e.g. "The dashboard will be unavailable for up to 10 minutes within this window." If there's no visible impact, say "No downtime is expected."]
What you need to do: [usually "Nothing." If there's action needed, put it first, not here.]
We'll post progress on our status page: [link].
When it starts
Maintenance in progress
Maintenance on [system] has started as scheduled. Expected completion: [time].
When it's done
Maintenance complete
Maintenance on [system] finished at [time]. All services are operating normally. [If it ran long or impact differed from the plan, say so in one sentence.]
Rules
- State the window in a named timezone and, if your customers span regions, two ("14:00–15:00 UTC / 09:00–10:00 ET").
- The window is a promise. If you might overrun, book a longer window — finishing early delights, overrunning erodes trust.
- "No downtime expected" and "no impact" are different claims. Only say the one that's true.
- Cancelling or moving it? Notify with the same visibility as the original announcement, not quietly.